So I'm thinking about getting a Lumia

Hey guys I need a new phone purely for my business. I already have an iPhone 4s for personal use. I'm seriously considering a Lumia either the 800 or the 900 I would wait till windows 8 is out and see whats available then. But i need it within a month or so. The question is which do I go for? In the UK they're both pretty much the exact same cost so what I'm really asking is, is there any particular advantage choosing say the 900? Any opinions would be appreciated.