I think for typical JS/CSS/HTML sizes, and decompression times, probably maximum compression ratio, followed by decompression speed is what I'd look for. I don't care too much about compression speed, in the sense that if I have to spend 1 minute compressing JS to crunch it by 10%, but I serve that file a million times, then as long as decompression doesn't negate the gain in network time saved, it's a win.

I guess the other factor for mobile is, besides memory and decompression speed, how do various compression schemes fare battery wise?