Honestly, the difference between mac and bbk headers are not going to make a lot of real life difference in performance. Nothing worth writing home at least.
You need to base your decision off of quality and longevity, especially if you're under a budget, which you are, or you'd already have the bassani's installed.
The bottom line is, the "majority" of mac headers have serious problems with re-installation. My buddy had TONS of issues re aligning them every time. Finally they cracked, and that was that.
simply put, you will NOT have those issues with the bbk headers. they're of a fantastic quality.
honestly though, for a little more, you can get the stainless ford racing headers. Nice pieces. summit has them for $225ish. I bought the ceramic units for $309, but I'd def do ford racing or bbk.