I use a SpA QR. The involute spline geometry ensure that you a) can only put the wheel on one way and 2) you have a very large amount of surface area--therefore given the same initial tolerances and materials used the splined unit will last longer.

I am very picky about my steering system's lack of slop. After all, how are you supposed to give/receive accurate input/feedback if you have slop in the wheel?

I have never felt a hex type without some amount of play. Some are much better than others and I recently inspected a car that had a relatively tight hex unit---no brand anywhere on the unit though, so I can't help you there. It had a 360* pull to release ring, was steel and the hex piece on the shaft had a large dimple machined into each facing.