It's been my experience that the rod balances better if you still use a downlocking seat and that very little extra weight provided by the bark grip is only going to help with balance. This is assuming that it's not a shorter rod that you're finishing out. My answer is predicated on rods that are 7.5ft and longer. Something like a 7ft 3 or 4wt I might opt for the uplocking seat so I wouldn't have to look for an ultra-light reel to keep things well balanced.

That's easy for me, I just never got fond of uplocking.