the BI Pro is a revised BI Prime. it has 1/2" fittings and makes 2 passes instead of 4 like the Prime (lower pressure drop as a result).
so instead of 3 parrallel channels making 4 passes, it has 6 channels making 2 passes. this should lower the velocity of the water, which increases the time the water spends in the rad allowing it to disipate more heat to the fins. if you look on the specs from
HWlabs, they do say it has better performance than the BI Prime.