The 285m is the faster chip, but I don't know if it is too old to play a lot of games driver wise.
The 500 series chip is one generation old (nvidia is on 600 series now) and the 200 series chip is like 3 generations old now. Not sure why, but I think Nvidia skipped the 300s for some reason.
Anyway, I would hazard a guess that the 500 series chip can use DX 11 and the 200 series chip can only use DX 9. That would be a big handicap going into the future.
I would honestly be worried that both laptops will perform below your expectations for gaming.
Anyway, I guess I would take the one with the 540 if it were me, to make sure I had DX 11 available.