Lenovo vs. MAC.. ah.. depends on your budget. A MAC running dual boot Windows and MAC OS is a good thing, and works well. Lenovo ThinkPad is as solid and sturdy laptop as you can get, but even those top of the line systems are cheaper than a MAC Pro.
If they were the same price, I'd get the MAC, although I am by no means a "MAC guy". But I would for sure get a dual boot setup for the MAC.
For PhD, also you may want to have a MAC. Many research instututions use MACs, so good to know the system, many programs used in such also run on MAC platform. Now that I'm talking about it, even if the cost was a few 100 more for the MAC, you may be better off with the MAC. Plus you can be all cool when you whip it out at Starbucks to check your Facebook :-)