I apologize for asking line questions all the time, but I really like it when a rod and a line come together and something special happens. And, since I've been on a glass buying spree, I've been asking more than my fair share of questions.

I recently received an Orvis SFG 7'6" 4wt. I had ordered one a couple months back but it had some cosmetic issues and I just could never find the right combo, so I got rid of it. Now that I'm going deeper down the rabbit hole, I thought I'd try it one more time. Here's what I've discovered...

I seem to cast it best with SA Amplitude Smooth Infiniti WF4 (actually 4.5) and Orvis Hydros Superfine WF5. Other lines included:
406 WF5, SA MPX WF5 (5.5) and Cortland Sylk DT4. The MPX formed nice loops and was good up close but I felt like I was having to push the rod. The 406 and Cortland Sylk just didn't respond.

I've thought about buying Cortland 444 Peach in a DT5 just to try something different, but could also just be wasting money.

Here's what I don't get...the SA Smooth Infiniti WF4 and the Orvis Hydros Superfine WF5 have very different profiles. The SA has a 48' head with a long belly and a 6' taper. The Superfine has a 37.5' head with a 17' belly and a 9.5' taper. It seems in some ways that the two are significantly different. Which leads me to ask...why do they seem to perform equally as well with my casting stroke? My test casts ranged from about 10' to 30', with the sweet spot for both being about 25'

So, ultimately my question is what line do you find works best with this rod for general purpose work? I have both SFG 3wt's already dialed in for really tight quarters and would like this one to be geared more towards actual casts with about 70/30 dry fly/nymph or bugger. Why do these lines seem to work and do you think there's a better choice? Might I be better off with a 444 Peach DT5 or a 406 DT5?

Thoughts? Musings?

I liked Rio Gold wf4 and SA Mastery Trout wf4 with that rod. I’m my hands, 5wt lines were not the ticket.

The 4wt was the first Superfine Glass model I bought, and I purchased it as an outfit, which came with the Superfine 4wt line and a Battenkill reel. It worked great for me. Granted this is the older model of the Superfine lines.

Another line I like with it is the Airflo Xceed 4wt, which is a half weight heavy, and textured. Again, this is the older model of the line. It can work reasonably well with some 5wt lines, too, as you've noticed.

These things are all pretty subjective. I hope you enjoy your new rod !

I wouldn't use any DT5 on this rod unless you'd only be using the first 30ft of line. Beyond that it will quickly overload the rod. A "true" WF5 will work but best at close to moderate range. Any long distance casting you should use a half heavy 4wt. I like it best with a WF4 Rio Gold or WF4 SA Frequency Boost.

At 10' it's all leader and rod, so the line could be a #12 and not be much different, even at 30' there are only a few feet of untapered line in the equation and not more than a few grains different between any of the lines. I'd be surprised if anyone could tell a difference in the weight of the various lines. Take a standard #4 @129grains and a #5 @140grains, at 30' there is a 20grains difference on a scale, with the #5 weighing about the same as 4 USA dimes and the #4 weighing about the same as 3 1/2 dimes, so as an experiment take 3 dimes in one hand and 4 dimes in the other hand and notice how much heavier one hand feels, that's about twice the felt difference between the #4 and #5 at 30' or about 4-6 times the felt difference between #4 and #5 at the distances you mention.
If you carry the full head outside the rod tiptop in an over head cast you would notice a greater difference, but I would expect most rods to carry 40' of any of the lines about the same because even at that distance the mass loading the rod are not greatly different, add 4-5' to the length of the lightest line and the mass will be close to the heaviest line. The profile differences are more about where on the line that mass is located and in my thinking have less impact on felt loading or distance cast than the marketing people would have us believe. Profile might make a great difference in how the fly lands but that can be more affected by the leader used.
What I'm trying to say is that I think you are looking for a greater difference than you are likely able to feel. I'm not very sensitive, but if you put the entire line of each of those lines you mentioned into identical containers like a paper cup or a sock, I could not differentiate between them by feel.
I'm a mediocre caster even after 46 years of fishing with 'glass fly rods, because it was all fishing and very little casting, but, I'm guessing that I could fish any of those lines in #4 - #6 on that rod just because I don't have high expectations and my stroke is variable. I'm sure that after using each of the lines to catch 10 or 20 fish with #16 - #2 flies that I would prefer one or two of the lines over the others.
My advice is pick one that has a nice color and spend about three days on the water with it, then chose another and do the same. I'd also advise a ~7' 5X leader for fishing with the short rod, and if using extruded leader I'd cut the butt down to where the diameter is ~0.017 rather" than 0.021"-0.024". In my fishing, leader seems to have greater effect on my cast than line or rod does.

Ultimately the presentation predominantly depends on the fly/leader combination. I can use a level line and use a hand tied leader with a much heavier than usual butt to more or less duplicate a DT........

When you test a bunch of lines like that your preference will be partly formed by the order in which you cast them and what you had for breakfast that day.

After two or three days of fishing any one of those lines and adapting to them you would probably be quite happy or at the very least effective.

Just choose a line that feels reasonably good and whose taper makes sense for the fishing you do and use it. No need to overthink it.

If you are absolutely going to nit pick asking third party opinions isn't going to be very useful because you are the one who is being finicky - no one can tell you what your tastes are.

I have to say that my approach to testing a new rod with different lines is completely different: I buy my favourite fly line tapers in a range of weights (SA Trout in 3 to 8 WT and SA DT in 3 to 6 wt). I will then try a couple or three different weights on the same rod - but I am keeping the line design more or less constant (different weights in the same line will have slightly different head lengths and front taper lengths). This gives me feedback on how the rod will feel and cast with different line weights and I form an opinion on when I want to use one weight or the other. I stick to a line design that I feel is sufficiently versatile and appropriate for the fishing I do.

This is a very efficient way of having a mental reference of how the rod behaves and helps me learn it very quickly. If I then try a fly line with a different taper design from my reference lines, I am able to differentiate between the effect of the taper change and the effect of the line being half a weight lighter or heavier. This helps me decide quickly what the strengths and weaknesses of any specialty taper might be.

This is kind of genius.

Casting on water is the best way to get the feel of a line, not only how it casts, but how it handles in common fishing moves such as mending.
The line has to be wet and picked up off water. If you pick up off grass/gravel/pavement, you'll adopt a different style to avoid herky-jerk loading. Or you'll wind up carrying line and making unnecessary false casts. You can throw a low loop to lift the line off the ground, just as is often done to avoid disturbing the fishing water on pick-up, but the feel a dry line still won't be the same, in the fingertips or through the guides.

I really appreciate all the thoughtful replies.

To answer a few questions.

Yes, I had a standard 4x tapered leader that probably started as a 9’ and is about 7.5-8’ now. To the end of that was tied a piece of mop fly chenille.

I realized today that the Cortland Sylk I tried the other day was likely a WF4. I tried it again today with a DT4 Cortland Sylk and it seemed to do better but not necessarily better than my other two. Up close I could tip cast ok, hit a sweet spot around 25-30’ and kind of fell apart past 35’ (the same is true for all lines on this rod)

I’m leaning towards the SA Smooth Infinity but given that I don’t see bombing long casts I wonder if a DT4 would be better? Something with a shorter tip than the SYLK or 406, like a Cortland Peach 444?

"Up close I could tip cast ok, hit a sweet spot around 25-30’ and kind of fell apart past 35’ (the same is true for all lines on this rod)"

This is a powerful 4wt rod, some think it's closer to a 5wt.. Although not the best tool for long distance casting, with the right line and normal casting technique it will cast well beyond 35' with good loop shape.

Interesting giogio, decades ago I found that nearly all extruded leaders were improved by cutting a foot or two off the thick end til the diameter is ~.017-.018" and nail knotting to the line at that point, but I had not realized that that was line brand related, I was using Peach and Triangle Taper (very long front taper, all taper?) at the time and just assumed that all line brands would be of similar diameter at the taper end of similar sized lines, like the old letter designations would indicate.
So many of the "rules" of leader construction and use (like the 0.002" max step down) came from the use of "gut" that I guessed the .021"+ butts were a holdover idea too. On my 4wt & 5wt lines I generally use 0.015" butts.

I had good luck with the 406 DT line as well as the Orvis Clearwater WF--both seemed to cast fine for me

The SFG isn't a slower rod. It's almost ridiculously fast for glass, which is probably why he liked it better with the heavier weight lines when lawn casting. As others have pointed ou,t though, water loading changes the whole feel.