I use both, the other day I ordered an Autometer water temp gauge for my Dart from Summit as my old one failed, I went to my local speed shop to get one instead, they had one in stock and after tax it ended up being the same price as Summit and I had it and didn't`t have to worry about it getting here in time for racing this weekend. I called Summit to cancel the order and it went fine. I have however had trouble with returns to Jegs recently resulting in more than an hour on the phone. Summit appears to be better in that situation. Shipping seems to be taking longer from both lately as they appear to not be stocking as many items and are having items shipped directly from the manufacturer.