Depends on the application. Dual channel has faster access, but most of the time it's the AMOUNT of RAM, not the SPEED.
I went from 512MB (2 x 256) to 1.5Gig (2 x 256, 1 x 1gig) and it's MUCH faster in everything I do... But, I think it's still using Dual Channel on the 256 sticks, as it...