Hey,
I'm not a Mac owner (yet) but pretty much in your situation as I'm planning to switch soon.
I was also in the same case in deciding which Mac I was going to get, MB or MBP.
1st thing I did is figuring out what is my use of a laptop (email, browsing, listening music & watching movies, instant messaging/skype, typing report for work/uni). Well pretty basic tasks as you can see.
2nd, I thought about what kind of laptop I wanted to have in terms of size. Currently I have a Dell 14" and I really want to have something smaller for easy carrying when I have to go to uni (almost going everyday).
Based on those 2 points, I found out that the MB would be perfect for my needs and use!! Althought at the beginning I was really interested in getting a MBP, then I thought about the price differences. Ok the MBP has an aluminium case, a better video card & some nice features such as multi touch trackpad, illuminated keyboard, firewire 800, DVI, etc
It would be nice to have all of those but only if you really use them
For example, I'm not really using DVI or any firewire peripherals, as I'm not doing any heavy photo/video editing or game I don't really need a powerful video card
What I'm trying to say is just that to make your choice, I would recommend to:
1: what are your use and needs for a laptop
2: what kind of machine you want
About what you say, I definitely think that a MB would be perfect for you!
Between the middle of the road MB and the black, except the color and the size of the hard disk, nothing's different. If you don't really care about the color and the size of the disk just go for a White MB (which already has a big disk)
Hope that helps