Marshall Defense 1.d4 d5 2.c4 Nf6 — transpositions I know that the theoretical refutation of 1.d4 d5 2.c4 Nf6?! is supposed to be 3.cxd5 Nxd5 4.Nf3.  

Perhaps Black doesn't fear the refutation because he intends a gambit such as 3.cxd5 c6?! or 3.cxd5 c5?!.  

My question is not about the refutation or the gambits. My question is, what if White declines to capture on d5, and plays 3.Nf3 or 3.Nc3? Does the game simply transpose into a normal line?  

In that case, has Black gained or lost anything because of his funny move order?  

If White is not going to play 3.cxd5, does 2...Nf6 have any advantage over normal moves like 2...dxc4 or 2...e6 or 2...c6 or 2...c5?
If you don't take on d5, I think the only advantage black has gained is flexibility. That means he can choose his opening according to your move. But you can be almost 100% sure that the opening will be transposed into some traditional line so white can't be worse, for example:


Slav Defence:

[FEN ""]
1. d4 d5 2. c4 Nf6?! 3. Nc3 (3. Nf3 c6) c6 {with the possibility of both Semi-Slav and Classical Slav Defence}

Queen's Gambit:

[FEN ""]
1. d4 d5 2. c4 Nf6?! 3. Nc3 (3. Nf3 e6 (3... dxc4 {Queen's Gambit Accepted})) e6 (3... dxc4 {Queen's Gambit Accepted})

Grünfeld Defence:

[FEN ""]
1. d4 d5 2. c4 Nf6?! 3. Nc3 g6



and there are probably many other transpositions...



In my opinion you have no reason not to play 3. cxd5. The position after 3... Nxd5 4. e4 (I think this is logical and even better than 4. Nf3) is very comfortable for white. You have a great center and black has to lose time again...