How can ANYONE hate i305? (Unless they rode it with the trims I guess).
Each company is great in their own right, but I feel like Intamin has the higher ceiling. Their rides also seem a little more unique. They're also the company more willing to try "out there" ideas, and as a result they also typically have the more intense, faster, and taller coasters between the two designers.
I've never once ridden a bad B&M coaster -- they're always quality rides. As for innovation, B&M just kind of comes in later to improve upon or perfect the forerunners' designs (this isn't necessarily a bad thing, however). Still, they're sprawling layouts typically have an almost artistic grace to them (see: Manta) and their smoothness is unparalleled.
All in all, however, I have to go with Intamin. They're responsible for my top 4 favorite coasters of all time.