Hard to get any clear info on these things, but my impression is;
1. Gt540m definitely holds the advantage in gaming.
2. Lenovo generally scores high marks on ergonomics and apparently the t420 is a solid performer for general computing.
Don't think you really need a gt540m for SH4 though; it supposedly runs current games on medium-high settings at 1360x768. SH4 isn't all that demanding. Still, if you plan on doing any gaming at all it's nice to have a half-decent chip powering it.
Basically, I'd say grab the Lenovo for business or the Asus for gaming. You'll have to decide yourself where your priority lies.
