Pirc VS Czech Pirc - Which Is Better?

The idea behind the c6 "Pirc" also called Prybil or Czech (Because IM Prybil is actually Czech :) is completely different than Pirc. Whereas Pirc focuses on Black squares with g6, the Czech focusses on Light squares , c6 with an early Bg4 exchanging the Bishop then playing d5, e6 without having the bad bishop. After 3...c6, white can play f4, then Black may play Qa5 and if e5 then Ne4, following with the regular plan if possible. Note that Petrosian played this system, a game which is analysed in the only book I know about this opening which is 1...d6 by IM Lakdawala. In my opinion this opening is playable and has less theory, could bring the 1.e4 player out of his comfort zone...

I'll try to re-use it. Lakdawala's ... d6 book is based on it.