In my trials of gut/poly versus poly/gut, I've noticed that spin and power are better with gut mains. However, directional control, especially redirecting shots, suffers.
The spin is actually too much for my liking with gut/poly, except I do like it on serving kickers. My issue, is that I am still too much of a flat-hitter. For that end, neither setup has ended up being my personal choice.
However, for those looking for comfort and spin, gut/poly is worth a few tries (it may take a couple to dial in proper tension).
Head Pro Tour 280/630, MP 18x20. Tour Bite 18/Mosquito Bite.
Sampras serve, Agassi backhand and Federer forehand. heh heh