At the present time without riding many Intamins (Stealth, Rita, Shockwave, Colossus and Indiana Jones at DLP) I can safely say the B&M's i've ridden are better.
Intamin appear to do airtime far better than B&M i've heard though. The Intamin Megas are apparently superior to their B&M equivalent. It all depends if you prefer ejector airtime (Intamin) or floaty airtime. (B&M)
Intamin do launches, B&M don't, Hulk is the only exception to this, but some people consider it a lift hill that increases speed rather than a launch this would be rather dull if there wasn't a zero g roll and a brilliant layout after it. Compared to a Intamin hydraulic launch which really is the highlight of most of them apparently.
B&M do inversions better Colossus simply doesn't compare to the likes of Kumba, Hulk and probably Dragon Khan. Intamin looping coaster trains are horrible and the ride itself just isn't as enjoyable as a similar B&M ride.
Don't give me that crap about Intamin being unoriginal either, nobody complains about the various Batman clones or Superman Ultimate Flight Clones. Anyway the park orders the coasters. Do you really think Intamin would turn down a sale? Neither company would, and to be fair I think this http://www.rcdb.com/ig3245.htm
looks more unique than any B&M i've seen. All inverts bar Nemesis and a few others do literally same thing, Drop, Vertical Loop, Zero G roll, etc.
To be fair, I personally think this poll is kinda biased with this being an AT forum, people will vote for B&M as Alton have 3 ranging B&M's, compared to 1 below average Intamin. Go to a Thorpe forum and everyone will say Intamin, due to Thorpe's 2 Intamins outnumbering their lone B&M.
I'm gonna abstaine from this poll, as I don't think the 5 Intamins i've ridden don't really compare to the 10 B&M's i've been on.
If I get on some more of the better Intamin coasters like Expedition Geforce, Goliath or Superman Ride of Steel i'd judge then. If I had to choose which company I prefer on rides i've currently ridden i'd go for B&M, but until then i'm not voting.
And please don't judge Intamin by Colossus and Shockwave. Despite the roughness Colossus is a good ride. And Shockwave is just as bad as the old B&M Stand Up's such as Iron Wolf and Vortex.