Say, average, 500 line PBP code will run significantly faster on 18F or not?
I don't care for banks or whatever with 16F - compiler takes care of.
I get that YOU don't care for banks or whatever, but the compiler does.

The answer depends on what your "average 500 line PBP code" does.
As you see from your original example of toggling IO ports, the difference could be anywhere from 0 to much faster.

How much faster?
It depends.