Okay - from the standpoint of basic motor design -
The B20 has a more favorable bore/stroke combination for high RPM engines. It also has more displacement, which = more power, all else considered equal.

As for the bottom end, an LS crank, an Eagle crank, and basically any B-series crank will fit. No matter which crank you use, for N/A, it should be fully lightened, knifed, and balanced.

Further, because of the bore size, less dome is needed to get the same displacment on the B20. Not to mention the valves can be deshrouded much further with 3 mm more bore, so the airflow on the head becomes better....

How many more advantages would you like me to list?