Portability is the
only reason to get the MB over the new mini. If you take out the portability issue, it's the mini all the way
Here's what you get with the mini:
1)More ports -
very important. Way more.
2)FW800 - whoa!
3)vastly better expandability options - you can hook in more external monitors (2), instead of being stuck with the stupid MB screen. You can get really nice big monitors pretty cheap these days. Also, you can hook up with any number of keyboards, some of which will be better than the MB keyboard, mice etc.
And you're not paying more money (maybe even less) for the mini + externals compared to the MB.
Really, why get the MB? If you answer the obvious - "portability", then I'd say you are better off with a MBP, since that's a better computer and still portable (of course, you pay more $).
If you don't need the portability, go for the mini. If you need portability, go for the MBP. If you need portability, but can't afford to get the MBP, I guess you're stuck with the MB, and then I feel very, very, very sorry for you.