i use Chrome, i have firefox installed just to check if a sites template looks ok in it.
Why Chrome?
1. because i'm really used to it already, i know all the hotkeys and i like theyr shortcuts, some which ff doesn't have
2. it just loads like 10 times faster then firefox for me... i have a slow comp.
and if i want to do something fast... i just can't wait for firefox to load... i'm going banannaz