I used a Mac laptop for years (PowerBook 12") and, although the OS was pretty good (that's high praise from me) from a user perspective, the hardware was awful.
Aluminium is not an appropriate shell material for a mobile device. Being able to swap the hard-drive is essential, unless you want to buy a new device each time you drop it.
The Thinkpad is so much better than the Apple in every way. I run Ubuntu on mine, and it works perfectly.
The Thinkpad even looks better than a Mac. Not immediately out of the box of course (new Macs look lovely), but after a few months of use, the Thinkpad's magnesium alloy shell still looks pretty good, while a Mac's aluminium is scuffed and scratched.
No real scratches on it of huge amount, but aluminium as shell works quite nice thank you very much. I've had this laptop for almost 3 years now, outside of the whole case being warped around due to impact its pretty much same as it ever was.
On a tight budget, my kids use the much older x60 and x61 (on Ebay for about $150-$200), and even the (quite old) x40 and X41.