I've had the 172 and the Trophy now. The Trophy is better in some departments but likewise the 172 has it's advantages too. I think as your every day car, the 172 is probably the better option. The Trophy is very stiff and has the cup interior (Cheap) bar the Recaro's. For an out and out drive the Trophy wins by some margin, but driving like that is few and far between, well it is for me anyway.
I think the concept of the 172 fits me much better, a nice all round car which drives well and just so happens to be quick. The Trophy has a great feel and after the Mark Fish upgrade is phenominal in the corners but getting to those limits requires some balls. As it's so stiff the Trophy does inspire more confidence but you have in the back of your mind about overstepping the mark (Well, I do), especially when you're getting to its limits as by that time you're carrying alot of speed. The 172 as standard was much easier to push 'harder' at lower speeds (Well, perhaps you have that sensation you are pushing harder), as since it was so soft it would just start to understeer and scrub off speed. I don't think for me, there is much difference in how quick I actually make the cars go as the limiting factor in each instance is me. There is only a few places where I go quicker in the Trophy than I did in the 172 and they are all slow corners, not quick ones as you don't have to worry about skipping off the road.
Straight line speed does have some differences. The 182 picks up much quicker from low revs and is noticably better. However, when in the band there isn't much in it. I used to reguarly race Paul in his black 172. We both had sports exhausts, however he had an airbox and a RS Tuner remap - ok there may be some argument for saying he should have the 'slight' edge, but there was literally nothing in it to high speeds. Not enough to make you think I'll have one over the other.
All in all, unless like a Williams, you 'want' a Trophy, I'd be inclined to stick with what you have. Or if you are going to swap, consider a Megane.
