I think if you are playing the Lopez as black, you should probably be studying quite a few of these positions
Anyway, I think it's more comparing the Bf8 vs g6 and Bg7. Bf8 doesn't weaken the kingside and the bishop keeps some hope of activity elsewhere - the Bg7 can be rather passive.
In comparing the Breyer position I'll say I think that having Bb7 and Nbd7 vs Bd7 and Nc6 favours black when the bishop is on g7. Everything is better placed for the ...d5 break which makes it harder for white to maintain the tension.
Also, white can try to take advantage of black's ambitious move order. Lines I've looked at that I think are possible promising for white are:
5 0-0 Bd7 6 d4 Nf6 7 c3 g6 8 Re1 b5 9 Bb3 Bg7 10 Bg5!? which Taylor is dismissive of (via a different move order). However in my database of TWIC games I see white going +9 =3 -1 here, with Navara, So, Alekseev and others bashing the likes of Malaniuk, Mamedyarov and Sadvakasov.
5 0-0 Bd7 6 d4 Nf6 7 c3 g6 8 Re1 b5 9 Bc2!? also looks promising. 9...Bg7 10 Nbd2 0-0 11 h3 Nh5 is Taylor's only line, but 12 Nf1 h6 13 Ne3 transposes to Kobalia-Naumkin, Moscow 2009 when 13...Nf4?! 14 Nd5 seems good for white already. I don't think black can get away with kingside activity while the tension remains in the centre.
Anyway, I've decided that I prefer white in this variation although it's playable for black, and that Taylor's book raises more questions for me than it solves. I doubt I'll play this in serious games.
NeverGiveUp wrote on 05/26/11 at 10:43:21:
NeverGiveUp wrote on 05/26/11 at 09:45:05:
Along these lines I have been playing 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.d3 g6 6.c3 Bg7 7.0-0 0-0 8.Nbd2 b5 9.Bc2 Bb7 for a long time, where you get a classical main line RL type position for black with the bishop already on g7 so with a few extra tempi for black, in particular if white goes d4 afterwards which he usually does.
Sorry guys, his line should read 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.d3
d6 6.c3 g6 7.0-0 Bg7 8.Nbd2 0-0 9.Re1 b5 10.Bc2 Bb7
Marin used to play this way as black with great success, but in A Spanish Repertoire for Black he is quite pessimistic for black after losing badly (he admits this is subjective, and gives the game with light notes). It's more accurate to say it is a tempo down for white on the variation we are discussing i.e. 4 Ba4 d6 5 0-0 Bd7 6 d4 Nf6 7 c3 will eventually transpose, except with d4 instead of d3 for white.
Even assuming he is being too pessimistic here, I'm not sure I'd want to give white an extra tempo...