Hi,
Recently I've got just a pair of 6571 and considering getting some other ones on the Bricklink, such as x873c01, 11949, 11950 or 92908c01. There is one more option to go - to make a custom wheel hubs from Lego parts using single axle connection (I prefer using 44772 56mm D. x 34mm Technic Racing Medium wheels). I heard some complains about the 11949, 11950 so instead of getting them all and testing by myself I decided to ask what do you think about them all?