As far as I know 3...h6 is the "standard" move order, though I've seen 3...Bb4+ 4. Nd2 h6 (and Seirawan-Portisch) cited as equal.

Vass wrote on 03/25/13 at 11:54:57:


Well, it could be mentioned that three of the four games transposed to the Nimzo, and the one that didn't looks to have been between a player rated in the 1800s (FIDE) and one in the 1600s (DWZ i.e. German), and on a website where engines aren't allowed.
 
Incidentally this was the second instance of "what should I play against 3. Bg5?" in the last couple of weeks -- was there a recent internet video advocating it or something?

and what's the advantage of 3...h6 4.Bh4 Bb4+ versus 3...Bb4+ ?

Fully agree with what MNb wrote! 

@ gramsci

You'll have to go through some games, for example: Avrukh-Gulko (Istanbul 2000), Seirawan-Andersson (Tilburg 1983), Sichinava-Rakhmanov (St Petersburg 2011), Dzagnidze-Hou (Beijing 2011). Abdulla-Neverov (Sautron 2001). All of these go like this 1.d4 Nf6 2.c4 Nf6 3.Bg5 h6 4.Bh4 Bb4+ with the idea of c7-c5 next (4.Bxf6... or 4.Bf4... are considered to be inferior to 4.Bh4..., so making your repertoire against these moves would be easy for you).
In addition I'll post here some correspondence chess games that can't be easily found in the well known databases.

There's a guy in my club that always avoids the NID this way. What do you think is the best to face 3.Bg5: 3...c5 a la Benoni, or 3...Bb4+ allowing white's 4.Nd2? Where I could find information?