If speed is not a factor (either because you're not interested OR your laptop is not capable of dual channeling) then buy the cheaper 1 Gig module. The manufacturer is not so important but the caps of the module ARE.
I suggest using Everest to determine the RAS-CAS lantency caps for your current RAM and choose an additional one that matches those. Ie, it works 2.5-3-3-7? Then buy a module which works at the same speed. This way you get the smoothest operation.
BTW. Infineon is a middle-range brand but one of the best among them.
Remember, the more memory, the shorter is your uptime, even if it is a less-power consuming DDR (DDR2 eats more). For a non-gaming laptop, 1 Gig should be enough for everyone
