It's hard to get or give numbers, but by just looking at your two choices I would say that the fentons flow better. BUT, I would not give up the exhaust heat to the intake manifold for a street driver. Corvette duel exhaust manifold is REAL hard to find and they usually go for over $600+.
I would go for the "Kansas Kustoms" split. http://www.kansaskustoms.net/