The 6mm connectors work very nicely and using connectors make for easy maintenance and changes at the track. According to my Fluke DMM, the use of the connectors added no measureable increase in resistance. I don't know if that would change if current was passing through the connection at the time of taking the measurement, but I haven't had any signs of any problems. I haven't had any cogging or signs of the connectors heating up. What I have noticed heating up is the 13 gauge wire that comes on the MM esc. Since I went with 12 gauge, I haven't had any problems with that either.