On one of those horsepower shows they said to be sure the grease fitting is in a position so that the drive line forces compresses at the grease hole. If your U joint is clocked wrong, it can pull at the grease hole and possibly braking your U joint from being pulled apart.
Id get one with a grease fitting as you don't have to remove to lube and make sure its installed in the proper orientation.
thats something I never thought of before, but make sure its done this way every time now. That being said, The only U joint I broke was on install. lol