I would discount the Mac option as you have CS already for PC (unless it is a Wanchai Special).
I would steer clear of the Sony because they are a hassle and more expensive in the long run.
Someone mentioned Fujitsu earlier: an ex-colleague bought about 20 Lifebooks (?) for office use and they proved to be pretty solid and reliable. I think they are also a bit cheaper.
Otherwise you could look at the 2nd hand option.