The Benoni Defense is a solid, well-known opening at higher levels. The "old" Benoni move order may surprise the unprepared, but White usually just plays 2. d5 and play will transpose into the mainlines where both sides have thematic play.
As far as in the second diagram, White would rarely play 3. Nc3 because 3. c4 is still opening book and then Nc3 can perhaps be played later (without "blocking" the c-pawn like in the diagram line posted).
I think it's fine for most of us. What you'll find as well is that "system" players will avoid the best line of 2 d5.
As for the transposition to the Morra, I'd play 1d4 c5 all day long if white was to venture 2d4 :-)
This guy has some good stuff on Benoni lines:
The problem with the Old Benoni is that White gets a significant advantage by NOT playing c4. This leaves the square available for the King's Knight (Ng1 - f3 - d2 - c4), attacking the d6 weakness. The other Knight goes to c3, combined with a4 to stop ...b5. The Bishop goes to f4 against Schmid/Half benonis (e7-e6-xd5), and against the Closed Benoni (...e7-e5), there are other avenues for White that I don't recall the theory of as I quit playing d4 a while ago, and do not play this as Black. Only benoni I would play as Black is the Czech Benoni (1.d4 Nf6 2.c4 c5 3.d5 e5), though there is nothing systemically wrong with the Modern Benoni. The key thing is that Black waits for c4 before playing ...c5. WIth a pawn on c4, no White Knight is going to c4, and in the Modern Benoni, where Black has already developed a few of his pieces before doing ...exd5, White doesn't have time to swing the Knight around.
Its one of my favourite openings against black. I usually play it to punish those who try to play the queens gambit against me.
I think benoni is very good, but personally I prefer QGD, Slav, and east indian (I dont play east indian, but I like its concepts more than benoni.) over it.
Am I just stupid or is the Old Benoni Defense a solid way to surprise your opponent? For those who don't know what it is, here is the line.
I know that if White plays 2.d5, it gives White a spatial advantage, but if white opts to take on c5, or play e4, Black has a solid chance.
Alternatively,
I might just be mentally incompetent, but this isn't too bad for Black.
Please share your thoughts.