Chrome is much less transparent.

Less memory usage, faster JavaScript loading, faster JavaScript engine, sandboxing, nice UI, more W3C standards support (which means cooler elements and web interfaces), faster WebGL support and faster GPU communication as of the last few updates.

Firefox has lower memory usage.
Load times are about average for every web page on both browsers, both startup and webpage loading.
Firefox supports sandboxing, which will run in a seperate plugin container when needed.
Firefox has equal W3C standards support.
Firefox has equal WebGL and GPU support.
Because of the lower memory usage, Firefox still is winner.