Both are equally good.
But (it may seem surprising), Ba7 is more straightforward, with the idea Ne7-Ng6 following.
b5 could be play later.
But u know, after b5 now, black usually continue with the same plan above.
The reason not playing b5 is that it allows a4 for white i guess, so no need to give an extra option for white.
In the end I opted for 5.Bxc6 after 5...dxc6 I go for natural devellopment with 6.h3 and 7.Be3. At least this makes sense to me and works for me.
6.Qe2 isn't that surprising though when considering transpositions, its a pretty common approach following 5.Bxc6. Caruana, Giri, (Carlsen), and others trot it out.
Carlsen's 6.Qe2 is interesting. White creates a direct threat(Nxe5) and forces Black to find a way to defend e5 while remains flexible and he might even castle q-side. According to Svidler in this type of pawn structures Black's dark-squared bishops is not well placed on c5 so white in some cases tries to take advantage of this.
6.Qe2 maybe is an interesting alternative/surprising weapon.
You are very well informed as always. Thank you. But I couldn't help but notice that 10...Bb6 may prevent some problems. As for the article @poucin, black seems to make inferior moves in all games which allow great attack. It seems white has barely any means of creating pressure of its own. Fortunately we are all just mortals 
In hindsight early Be3 is a bit crude, because I agree Bc5 can get outplayed.
In fact white is creating some problems in these d3 Berlin lines, and other d3 Ruy lopez. Also creating difficulties in the Petroff Nc3 lines. White has more problems getting anywhere in the exchange Queens Gambit, semi-tarrasch and other Queens Gambit declined lines currently. It wasn't an accident that there was so many 1e4 e5 games in last world championship.
I don't play those other ones :) But I'll take your word for it. I guess the problem is that I don't enjoy the Berlin because I don't understand it well enough. But that is slowly changing :)
Ok, I tried a little harder and found some improvement: 8.c3 with intentions of putting a knight on f5 to start trouble while keeping the center in check. Here's the model game I constructed. It seems promising.
Can't say understand 8c3, guess it is stockfish or something, 8Qe2 with the intention of queen-side castling similar to games in article IM Poucin mentioned look interesting to me.
8.c3 is part prophylactic, part waiting move. It does some things like, giving b2 the protection of the queen and covering b4 and d4, to make play against Bc5 and to gain a square in the center. Also it lets black make a move so white can adjust its plan. Most likely black will rook, so then white can play it's knight to f5 to start an attack.
Please try to play around with it yourself, I found that white always has some way to get good play. Please let me know if you found a counter :)
Hi all,
When I was browsing an opening explorer to acquaint myself with the quiet variation of the Berlin defence, I encountered somewhat of a mystery to me.
In this position black used to play b5 and have good stats, but for some reason recently the common move has become Ba7. To me these moves both seem fine, although the masters seem to disagree.
Has anyone an idea as to what the underlying reason is for this?