Hmm, for me, chrome is a much bigger memory hog than FF. Its memory usage is somewhat more controllable because of the process-tab thing (which is probably also responsible for its greater memory usage), but while actually in use, it uses a lot more memory for a given set of tabs open.

Speedwise, they seem pretty much neck-and-neck, although chrome is faster at some of the advanced webgl 3d rendering stuff...

[The competition with chrome has been a great thing, as it seems to have lit a fire under the FF devs, and resulted in many, many, improvements in recent versions.]