I tested between Firefox 6.0.1 and the nightly build, and I think 6.0.1 has better loading speed than Fennec 8.0.1.

Another problem on Fennec 8.0.1 was flash-contents display. I downloaded "libflashplayer.so" and put it in my mozilla plugins directory, and Firefox 6.0.1 can display flash contents with a small red bar on the top (I don't know how I can get rid of it though.). But, flash contents on Fennec 8.0.1 are black-out and doesn't display flash contents at all. I even tried different versions of flash player, and that doesn't work neither; I extracted APK (Android Flash player) file using 7-ZIP, extracted only the flash player library file, and put it in my plugin directory, and it worked on Firefox 6.0.1 though.