If the total fan blade surface area is the greater on the 11 blade, and the blade pitch is the same as the 9 blade fan, than the 750 model has greater airflow capability. The next variable would be the fan clutch engagement characteristics.

I would think the 750 sedan has a more restricted airflow through the radiator and engine compartment than the E53 and would call for a fan capable of overcoming that additional resistance. On the E53, the 750 fan should provide a quicker heat transfer under high engine load conditions.

2002 X5 3.0 313,500 miles
2014 428i 23,600 miles

2004 2004 325i sold at 123,600 miles
2001 2001 325i sold at 66,000 miles

1970 Firebird Under restoration