I've had the benefit of owning/driving both on my 427 and it's hands down the single plane if... 1) you value performance over originality 2) you really want to rev your motor (6500 + - mine revs to 7600!) 3) you have a engine build to make use of the flow - ie. cam, springs, rocker arms, etc. etc. All in all I feel it is more tractable and a kick in the pants in a Cobra. I also had a 428 in my car for awhile - never again, I want horspower not excessive low/slow spinning torque. Rev it high and stroke it short and you'll have an absolute ball - guaranteed!
SOBRAC - The "parts for sale" engine is MINE - it's not being sold by Keith Craft - he just hand built it!
Enjoy your motor!