Lenovo ThinkPad X Series Tablet with 4GB Memory and Intel Core i7-640LM Processor,

or

MacBook Pro 13" with a 2.66GHz processor 4 GB memory.

Since budget is not a factor seeing that he works for the bank, he can swap the standard hard drive with a lightening fast Solid State Drive (I would recommend a Crucial RealSSD C300, but they tend to go for USD 750,but then again small things like cost is not a factor). The computer will be cooler and faster that he can handle or deserves. These SDD are like 50 times faster than the normal drive. Boot time either in Mac OS or Windows 7 will be reduced to less than 25 seconds.