There is no comparison; the 7250 is a much better BlackBerry. Twice the memory, better backlighting and Bluetooth - and it is faster also.
You will need to get the BlackBerry Data Service plan with your account; that is the only way to get e-mail onto a BlackBerry.
The included Desltop Manager program will allow you to sync your contacts, calendar, notes and tasks (via the included USB cable). E-Mail can be handled using the "BlackBerry Internet Service" (previously known as the BlackBerry Web Client), which is at no additional charge. It will poll up to 10 POP3 e-mail accounts (Comcast) and forward the e-mail to your BB every 15 minutes. Of course it may be possible to directly forward your e-mail from Comcast to the BB (when you sign up for BIS you assign an e-mail address to the BB - something like
).
There are several threads about good applications to purchase in addition to the included software.
Hope this gets your started!
Good luck!