Lighter parts, lighter overall weight, helps weight transfer, more room under the hood to work on it, might be cheaper and easier to get parts for. It's not always to be "THE" fastest. There will always be someone faster. As for speed, I've always run a small block. But I'm having as much fun or more running low-mid 11's now than when I was running low-mid 10's with my old Challenger. My current car pulls the front wheels better! It's also fun to try & get more from less.