I have found that using linear ESC's and one of them feeding the flight controller caused that particular ESC to get very very hot compared to the others. Switch mode ESC's don't give off as much waste heat when doing the voltage conversion down to 5v. So on my builds I've gone to using a separate switch mode BEC and disconnecting the 5v wire from all the ESC's. I don't think this is 100% necessary, but I'm hoping it will help my components to last longer and prevent an unexpected thermal shut down of one of the ESCs while in flight.