TSP limits the amount you can load PP#4, which takes some 'mass' out of the force created and lessens #3's transfer power.
Agreed that it is easier to master (a left hand karate chop to plane, focused on #2).
In a nutshell, TSP is less powerful, but more accurate.
Kev - a flat downstroke turn creates too much 'out', and makes it difficult to stay on plane.
If running down this plane can limit loading pp4, I'm assuming that kinetic link is affected (weaker) and the stroke must rely on acc1 to create speed.