My humble opinion....

The difference in hours doesn't necessarily equate to stick and rudder skills. As an PPL checkride pilot I have seen GREAT stick and rudder skills from PPL applicants with 40 hours. Of course, I have seen not so great stick and rudder skills at that same point.

However, the difference I see as a CMEL(commercial Multi-Engine Land) checkride pilot is in decision making and situational awareness.

Now as a regional pilot this is the biggest aspect, decision making. Training departments can teach you how and when to pitch, and push buttons. But they CAN NOT teach you how to make decisions and the different scenarios, abnormal situations, and emergencies you will deal with as a commercial pilot.

In the case of going from 400 to 800 or 1500 hours this is where you gain a lot of these experiences to have a base to make your future decisions on.

Just my humble opinion.