It's hard to say, but I voted B&M. Here's why:
While I do agree that Intamin has more OMFG-this-is-crazy!-type coasters (most of my favorites are Intamin), I just love the reliability of B&Ms. They manufacture some pretty fun rides! There are not very many B&Ms I don't like, but several Intamins that I don't really care for, and several that I like now, but if I rode them over and over again, I'd get pretty bored. However, B&M coasters are still fun even with repeated rides. I have ridden Medusa at SFDK soooooo many times, but I never get tired of it. It's just a fun coaster.
Other things I like about B&Ms: They don't appear too "scary" to most GPs, so I can usually convince the people I'm with to ride them with me; B&M coasters are pretty long-lasting (at least the ones I've ridden); they are very smooth; I like the variances of the inversions; but most of all, I'm pretty familiar with B&Ms and if I see one at a park, I know I can count on it to be a good coaster.
But like I said, I'm a lot more familiar with B&Ms and as I ride more Intamins, I might change my opinion.
“If toast always lands butter-side down, and cats always land on their feet, what happens if you strap toast on the back of a cat and drop it?”