As far as the axle they are all pretty much the same...where I have problems is in what attaches to the axle like the hubs. Previous to my Copperhead I had to over tighten the IRS left side hub to keep it from slipping and as a result cracked 3 of them right where the screw head goes through. The IRS left side hub on my Copperhead has not had this issue. I think it has to do with it being re-annodized. It just seems to hold better without using a gorilla grip to tighten it. I rather like the angle of the slot on the CRC axle better because when you tighten it up the 2 sides meet more flush and will have less propensity to crack. However the one I had the wheel screw holes were all crooked (Probably just got one that slipped through inspection). But I wouldn't worry about that as all the ones I have seen on friends cars since then have been straight. My favorite left side hub though was the thread on one that AE used to use. Never had to worry about a balance issue and it never slipped on the axle. The problem though was in axle spacing...there was pretty much only 1 width you could run with it. I also heard some people had issues with the threaded part coming out of the axle.