You could just run Linux on a macbook air..

That said, I have used macbooks and thinkpads and the aluminium might feel sturdier it is not. Drop a macbook and your looking at an expensive repair especially if it is case related, basically easier to buy a new one. Thinkpad parts are very plentiful and easy to repair yourself. And the cases may scratch but are not easely damaged.

Edit: I'm talking about the mid to high end thinkpads, comparable in price with macbook. The cheap ones are absolute shit.