I think all that matters is if a transit system has exclusive right of way lanes that doesn't interference from the general road network is what would make it fast. If it uses busses, light rail or heavy rail, the difference is only throughput.

For many people although LRT means a train sharing the road, sometimes, which make them as slow as busses, for a lot more money for something that doesn't have the same throughput demands, which I agree when I've tried out sf muni.