MIB has more aggressive spinning than Buzz, but it's really only once near the end. Unless you get hit by the opposing car, but even then it's not too bad. DH hates rides that spin but he loves MIB and rode it many times. DS was pretty timid about rides, too (last year - this year is a different story) and he also loved MIB.
I agree with the others who think MIB is a superior ride to Buzz - more interesting and challenging. My family agrees, though we all like Buzz, too.