It depends. I know a ~2150 female player who regularly defeats players up to 2250 with the plan ..Be7-g5. (vs. both the Closed and the Czech version)
I wonder where she was taught to play this passive opening so well.

1) What's the difference between the Closed Benoni and the Old Benoni ?
2) Is there an Open Benoni ?

I am thinking on taking up a defence (versus 1.d4) which features more rigid pawn structures, and playing it against not-too-experienced players. 
For I now think that it was not my best idea to use much of my time (for chess) studying really flexible defences (NID/BID, Caro-Kann), where White choosen set-ups usually involve different pawn-structures as well--at least not until I am rated at least 2200, and that it might worth a try to turn my attention towards less sound defences...


Here are my questions:

1) How the Closed (or Czech, if White chooses 4.c4) Benoni compares to the Dutch Stonewall?
(probabilities of White losing his way and Black's devices to exploit them)

2) Besides Palliser's very recent How to Play against 1.d4, a copy of which I don't own yet,
where can one find a thorough coverage of the _Closed_ Benoni? (1.d4 c5 2.d5 e5 3.e4 d6 4.Nc3)
(Chessbase article, NIC Yearbook, etc) 
(I already saw Andrew Martin's Fritz Trainer DVD on the _Czech_ Benoni.)