I think you are right in going for a fanless card - quieter and less to go wrong - as you aren't trying to wring max performance out for games.
The amount of VRAM on a card is not a reliable guide to performance, as most of it is used for geometry, texture mapping and effects in games - not something that you are overly concerned with. For most purposes, a 256MB card is just as good as a 1GB card (everything else being equal).
Of the 2 you have shown, I would choose the Asus, as it has a 128-bit memory interface. Not that much else to choose between them.
SD