You've also gotta consider the average leg length at the regional, number of takeoffs and landings, time in the terminal environment, blah blah blah. RJ's are doing the kind of flying that allows for WAY more mistakes than mainline aircraft. When you're entire trip consists of EWR-LAX, overnight, LAX-IAH-ORD, overnight, ORD-EWR-BOS-EWR and you're done, you've got way less oppertunity for mistakes as you're not transiting in and out of the terminal area as often.