It's subjective. They both net the sameish gains with different sounds out the pipe.

 

Depends on the diameter of your exhaust mostly

 

Think it's 2.5 pipeing

 

Since you're running one of Borlas finer true-dual exhaust systems a y-pipe isn't needed. Once Motordyne is established on the right coast you can buy/install one of there ART pipes but you may not like the smell/stench of your exhaust. I suggest instead you get Fast Intentions HFCs, they're better than Berk's and 48 state legal. Do not sell your OE cats, with the Feds making new laws hourly you may need to put them back on! Read all the stickys at the top of the coupe page...knowledge is power!
Gary