Overall I'd have to say Team17, although both were disappointing as often as not. Body Blows was way over-rated, it's like they came up with a reasonable engine without worrying about the actual game itself, Superfrog was massively disappointing (parallels Body Blows, but then so do most Team17 games), Magic Pockets was hugely jerky to a point it spoiled any chance of it being decent, Gods I never really liked, although it looked ok for an ST game (deliverance was far superior in my opinion). Both companies had as many or more average (or worse) games as good ones, but coated with nice presentation. It's for this reason alone I'd vote for Team17 of the 2, as thier presentation was a little better. Having said this though, of all the games released between the 2, my top 2 favorites are by Bitmap Brother, in Ruff 'n Tumble (one of my all time favorite Amiga games) and Xenon1. My favorite Team17 game is probably Overdrive.
Actually, thinking about it, when you throw Speedball 1 and 2 into the equation (which I forgot about when I typed the post originally) it goes someway to tipping the scales in favor of Bitmap Brothers. No question about it that Team17 had games that where more specifically Amiga (Bitmap Brothers after all developed for st and amiga most of the time), but in terms of pure gameplay, the better Bitmap Brothers games were more fun for my tastes.
