I have a HTC HD2 which is win 6.5, so can't comment on Android but the phone itself is a marvel. The HTC sense OS is the same on android and win, so I guess the real differences can be seen in lower level adjustments etc. how they work.
But, based on my experience my next phone will most likely also be a HTC, and I'd guess windows mobile as well, but I'm not averse to android either. However, the calendar app must work just like Outlook. The calendar is by far the most important app I use on my phones, and I absolutely loathe the calendars on every phone I've tried - even my HD2's own calendar sucks big time - so the most important thing for me is I must be able to run a real Outlook calendar on the phone.
By that I mean, I want the view of the day be like a drawn schelude where I can see boxes for classes and how they overlap and what kind of breaks there are with one glance, not just a list of things. It has to be boxes like in Outlook, very visual etc. and I must be able to move those boxes with my finger and edit them etc. as well, and be able to jump to any day with a sweep of finger and again see proper colorful boxes for lessons, not just lists.
So whatever the next phone is, it MUST have a proper outlook calendar, not just a sync. It seems like there are some apps with a proper calendar, like this looks a lot like the Outlook one and could work: