Jegs Vs. Summit
I buy from both and I've never had any big issues with either. When I ordered a rear disc brake kit for our Charger they sent me one without an e-brake but their eBay ad had it listed as having one. They had made a mistake when they wrote the item description. The e-brake equipped version was a few hundred dollars higher.
When I called them up they said to send it back to them (on their dime) and they'd send me the one I wanted at no additional cost. They were true to their word and they ate the fees. I'm sure that they took a loss on that sale but now they get the majority of my business.
AS far as the speed of shipping goes, it depends on where you are at in relationship to either one's warehouses. For me JEGS is often 1 day sooner arrival.