I'd have to say that the MBP's aren't quite as fragile as some people in this thread seem to think, though definitely less than a ThinkPad.
I personally use / abuse my technology pretty badly- my Macbook Pro 2,2 (non-unibody) is on its third battery (these are batteries rated for 300 charge cycles at 80% health- each of the first two has well over 400 on it) and it's nearly four years old. This thing's been slung into a backpack several times a day for most of that time, often squeezed in pretty tightly. It took a four-foot fall onto a dense carpet (the kind that's barely softer than concrete)
when the display was open, but it's still going strong. The screen did have to get replaced, but that was due to random failure more than anything (this was months after the nasty fall).
Don't get me wrong, I DO try to take care of it, and have it in a backpack with a padded laptop sleeve, but I'm not the kind of person who makes sure to keep food away from the laptop, or who constantly babies it. It might be a nice looking computer, but it's also a tool. And while it's starting to show its age- keys are starting to wear, etc.- it's still in relatively good condition, and I think it'll keep working for a few more years (hopefully until we get Core i9 MBPs with 1080p holographic displays.

)
Bottom line- if ultimate durability is your concern- yeah, go for the ThinkPad. But MBPs also aren't quite as fragile as some people seem to think either. Take basic care of it, and it'll work fine. You might get some random scratches and small dents, but if you're really looking at a ThinkPad, pristine cosmetics clearly isn't a concern anyway.
Oh, and to see what happens if you run over a non-unibody MBP with your vehicle:
http://forums.redflagdeals.com/what-happens-when-you-run-over-macbook-pro-pics-included-477582/
Darn thing still worked.