Windows 7 has smaller memory footprint and a much better UI. It's not sluggish like Vista, driver support is much better as well.
Leopard > Win7 > XP > Ubuntu > 98 SE > WinME >>>>>> Vista Thanks to Vista, Ubuntu and Leopard gained mainstream popularity. & Thanks to Win7 It's all coming back now with Snow being a minuscule update.
I am currently using Vista at the moment and I dont like it for some reason that I need to update it from time to time and their are a lot of programs with doesnt support Vista which is really irritating sometimes.. I think windows 7 is much better
I too vote for Windows 7. I've been using it for some time now (from the beta) and I must say i really like it (and I'm not a Vista hater like most other people here- i think it's a descent OS and a huge upgrade over windows XP). Windows 7 has great UI, works faster than Vista (especially with many applications opened at the same time), supports more hardware by default (less driver installations needed if you are not a perfectionist), shuts down very quickly and so on... Use it