Colt has a strong following and better name recognition and will command a higher resale value.
Bushmaster internal parts are more mil-spec (diameter size of the pins for the hammer, disconnector, trigger as well as the holes for the same, diameter of the pivot pin in the receiver).
I like both but if I had to choose one over the other for the money, I'd go with Bushmaster. If money wasn't a problem, I'd go with Colt.
------------------
Vigilantibus et non dormientibus jura subveniunt