Dxc5 is probably not the best to play. Black can respond with e6 (attacking the pawn) and from there white should give black the pawn back. If he plays Be3 then black can play Na6 and white cannot further defend his pawn while the bishops hinders the movement of the e pawn.
I think that 1. d4 Nf6 2. c4 c5 is a more popular way to play the Benoni anyway.
I've always had this doubt. Since I'm not so good a chess I couldn't imagine the idea behind this game. Can someone please help me out?
The following position is a typical Benoni Defense.
I didn't get why black pawn has to be pushed to c5, while it can be taken by the white pawn at d4? Tell me if there are any shortcomings if the white takes the black pawn.