I suggest the 8700. I used to be a Windows Mobile guy, and was totally won over by the BlackBerry, as many people in here were. It is just a much more stable device, reliable, it always works. The WM devices are not that fortunate. Granted, there are many more apps for the WM devices, but once you cut through most of the crap and ask yourself what you actually need as opposed to what catchy apps seem "neat," you will see the BB has everything necessary, plus some fun ones. For me, I need reliability. BB wins hands down in that department. I also need instant email - no contest with WM there either...
I also am a Mac user. Your options would be to use PocketMac to sync iCal, Address Book and To-Dos with your BB, or get a hosted BES to have wireless real time syncing through Microsoft Exchange and your BB. That way you can have access to a web-based Outlook to utilize with your BES, or you can get third party software to sync with (GroupCal and AddressX from www.snerdware.com)
. I use www.link2exchange.com
for my hosted BES, and others use ExchangeMyMail, MailStreet or some others.
The other thing to consider is the fact that most third party apps you want to load onto your BB will require the Desktop Manager software, which currently is only available on a PC. Though there are many apps that you can install OTA (over the air, no Desktop Manager required), but not all of them have an OTA option. I have a cheap Dell laptop to use for this purpose. But there are several members in here who do not have a PC laying around like I do. You can read a lot about it in the Mac Users forum here - http://www.blackberryforums.com/mac-users-corner/
Welcome aboard! I suggest you do a lot of reading in this forum, and ask questions when a good search turns up nothing.