I'm probably fairly typical here, I don't have a favourite because I've only tried one, its the original 1970 that uses rubber mounts from an Austin Mini exhaust system.
But I would like to know which is the best, so some kind of engineering assessment would be great. Or even an engineering discussion that would help people make a decision on which one to go for.
My assessment of the 1970 original:
Pro:
Its original, doesn't need maintenance apart from replacing of the Mini exhaust mounts every 40 years
Con:
It flexes in every direction, side to side, front to back, up and down, and because of all the flex in the joints, the rubber mounts don't seem to be too significant
Because there isn't much that can be done to improve things, even Norton replaced it in 1973.