There are so many different opinions on this one! However, the new Accufab plenum is a full 75mm internally as opposed to the original 70mm design. If you plan on staying N/A, you may not see any real performance difference between the two TBs. If you ever plan on running an S/C, go with the 75. For me, I always recommend a little overkill if it will not negatively impact anything else. You may not have an S/C in your immediate plans but never know - why buy twice?