Firefox all the way cause of all that SEO tools and stuffs + some other add-ons which i think IE and chrome will never have... well maybe someday...
I use only firefox because it far more better when compared with chrome when you open more than 100+ tabs..
I use all three browsers very frequently. FireFox is best for extra nice addons and most memory holding application. Crome is easy and less expensive in memory use. IE is oldest popular one and nice to use but can be hacked by most hackers Plus more crashing browser. Thanks