DID is way better
I have been using their ERV3 520 Racing Chain on the RC51, GSXRK5 and 2 1000RR's. One of them has over 14,000 hard, vicious, merciless track miles on the same chain. I don't know of any other 520 chain that can stand up to that kind of abuse and still look & perform like new.
Plus with complete 520 conversion kits starting at $225 you simply cannot beat the value of DID and AFAM etc. Sure you can find cheaper kits, but they will never last as long...
Prior to that I had used just about every chain brand you can think of and the only one that came even remotely close is Regina.