I was the owner of a black MB, but after numerous unsuccessful repairs, I upgraded to a MBP. The Pro looks 1,000 times better than the MB in my opinion, and no oil stains on the track-pad and such is great.
The MBP will dent and scratch pretty easily in most circumstances. I have a pretty thick Incase carrying case, and even a drop from waist level onto carpet (while in the case) will result in a dent. The dents are very small and really only noticeable due to the strain markings on the aluminum, but they are dents none the less. In terms of scratching, the top display case is the most vulnerable. If you ever set it upside down, even on a what you think is a relatively harmless surface, you are sure to get a scratch. The other parts of the casing don't scratch as easily, but contact with other metal (watches, other jewelry, binder-clips or paperclips on a desk) will but in a pretty noticeable scratch.
Is it that big of a deal? Not really. The effects of oil from your hand onto the black MB looks worse than a scratched up MBP in my mind. The top display casing of the MBP is relatively cheap (under $100 in some places) and I probably will replace it in a year or so. Obviously, if you are mobile all the time the MBP might not be the machine for you. The fact of life is, people will drop their MBP's and expose it to other damaging situations. Still, the MBP is a great machine, and looks GREAT with scratches/ dents or no scratches/ dents. The nice thing about scratches on the MBP too, is that they are really only noticeable from directly overhead in bright lighting. I would highly recommend a MBP to anyone.