I play Flash games on Chrome with an Ad-Block plugin. They run too slow on FF with or without Flash ads interrupting the game. I'm still using XP, so I would use IE 8 for games, except the dirty dog IE8 wants to scroll when I press the arrow keys for the game.
I added the Ad-Block plugin after the games became unplayable due to those stupid "Congratulations! You are the 100,000th Visitor" banners that blink on and off at 10 milliseconds in real time while probably not using any video buffer for the blinks. That behavior without a pre-render video buffer messes with the game.
I normally use FF for browsing. Like right now.