It's such a personal thing - the whole mobile OS is very much like the desktop OS - windows fans will always prefer it over MacOS, and VV.

I like Windows Mobile - it is by no means perfect, but it works, and it is mature enough that you can get things done. I find Android to be even better than Windows, it is much more polished, and the whole OS is just a pleasure to work with. That said, I don't know if any operator sells them in your country, so you'd probably need the Google developer version (which is unlocked and open).

That said - if you have your mind set on Nokia, by all means go for it. The N97 is an amazing phone, and I don't think it'll let you down.