There's only a handful of reasons to run 32 bit OSes and if you had one of those reasons you'd likely already know that you needed a 32 bit OS. Those reasons are a piece of legacy software that you have to have only working in 32 bit, a professional application (a lot of software companies will only help you troubleshoot their software if you're using windows xp/7 32 bit professional), or only having a 32 bit processor. Situations 1 and 3 are pretty rare though and none of the three sound like your situation.
As for which OS to use, if you already have 7 I'd stick with it. If you're paying for one or the other already I'd go with 8.1.
Every time I try to go where I really wanna be it's already where I am, 'cuz I'm already there XBL, PSN, Steam, Origin, BSN, GFAQs, MC: PhilOnDez