The overall feel of it. Great bearings beside the small driver one
The small bearing blows - literally. Hich leads to a number of bad things ending up with the driver blowing of locking up which is bad on high speeds.
I just bought my THIRD bi-rectional, 2 of the previous ones were used and the reasons for then to break were nmostly my faults in cleaning them. Don't use 19mm nuts with it, it will break the driver side cone nut and lead you to a world of trouble. And clean it occasionally. DON'T LUBE THE DRIVER'S COGS. The main reason i always liked the bi rectional is because it rides superb. But needs alot of work. Think of it like a supermodel girlfriend.