The Alpha three bladed prop specifically is designed for "trainer like" performace. Look at the blades, they are very wide and squared off, just for starters.

When you take an Alpha trainer and remove the 3-blade prop and put on an APC 10x7 or 11x5 or even 10x6, you'll find the plane has a lot more power, more speed and more climb. But it's not all because of the 3 vs 2 thing, it's because that particular 3-blade is designed that way.