The rd is better it is mandrel bent which is always better.....for all you that dont know what mandrel bent is it just means it does not have folds in the piping a mandrel is stuck inside the pipe to keep the bends smooth now personally I would go with a custom mandrel bent exhaust and a universal muffler that is true straight through design as opposed to the ones with little baffles or waves inside the muffler as they just disturb the flow of the air.....