In Christiansen-Zuger, I agree that 10.b3 is better than the plan chosen in the game.  I think black is well prepared to deal with an early queenside expansion like this.  As in the game, Black simply gained control of the center and white didn't have much to show on the queenside.  With a timely ...d5, it seems like black can easily limit the scope of the white-squared bishop, obtaining a favourable Tarrasch position (White's development seems too slow compared to a regular Tarrasch).

Here is the game:

[Event "Bern Cup"]
[Site "Bern"]
[Date "1996.??.??"]
[Round "1"]
[White "Zueger,Beat"]
[Black "Christiansen,Larry Mark"]
[Result "0-1"]
[Eco "A20"]
1.c4 e5 2.g3 Nf6 3.Bg2 c6 4.d4 exd4 5.Qxd4 Na6 6.Nf3 Bc5 7.Qd1 0-0 8.Nc3 Re8 
9.0-0 d6 10.Na4 Bf5 11.a3 d5 12.Nxc5 Nxc5 13.Nd4 Bg6 14.b4 Nce4 15.c5 b6 16.Bb2 bxc5 
17.bxc5 Rc8 18.Rc1 Qe7 19.a4 Ng4 20.Nf3 f6 21.Bd4 Bh5 22.Re1 Rb8 23.Nd2 Nexf2 24.Bxf2 Nxf2 
25.Kxf2 Qe3+ 26.Kf1 Rb2 27.Rc2 Rxc2 28.Qxc2 Bxe2+ 29.Rxe2 Qxe2+ 30.Kg1 Qe3+ 31.Kh1 Qf2 0-1

I think white needs to focus more on contesting black's central development.  I think the following game is worth looking at:

[Event "BEL-chT 9798"]
[Site "Antwerp"]
[Date "1997.??.??"]
[Round "4"]
[White "Cekro,Ekrem"]
[Black "Van Mechelen,Jan"]
[Result "1-0"]
[Eco "A20"]
1.c4 e5 2.g3 Nf6 3.Bg2 c6 4.d4 exd4 5.Qxd4 Na6 6.Nf3 Bc5 7.Qe5+ Be7 8.0-0 0-0 
9.Nc3 Re8 10.Qd4 Bc5 11.Qd1 d6 12.b3 Bf5 13.Bb2 Qe7 14.Nd4 Bg6 15.e4 Nb4 16.Nf5 Bxf5 
17.exf5 Qe5 18.a3 Bd4 19.Qd2 Na6 20.Rae1 Bxc3 21.Bxc3 Qxf5 22.Qxd6 Red8 23.Qe7 Rd7 24.Qe2 Nc5 
25.Bxf6 gxf6 26.b4 Nb3 27.Be4 Qe5 28.Qg4+  1-0

In the game, white played 7.Qe5+, but it amounted to a transposition to the suggested 10.b3 (after 12.b3 in the game).  This leads me to think that 7.Qe5+ is at most a transposition to 7.Qd1, which simply gives black more options.  I don't like how the queen is stranded in the center like this.  Also 7...Qe7 seems good after 7.Qe5+ as in the game Kosten-Collins:

[Event "BCF-chT 0102 (4NCL)"]
[Site "West Bromwich"]
[Date "2002.11.23"]
[Round "2"]
[White "Kosten,Anthony C"]
[Black "Collins,Sam"]
[Result "0-1"]
[Eco "A20"]
1.c4 e5 2.g3 Nf6 3.Bg2 c6 4.d4 exd4 5.Qxd4 Na6 6.Nf3 Bc5 7.Qe5+ Qe7 8.Qxe7+ Bxe7 
9.0-0 d5 10.cxd5 Nxd5 11.e4 Ndb4 12.Ne1 Nc5 13.Bd2 a5 14.Bc3 Be6 15.b3 0-0 16.Nd2 Rfd8 
17.Nef3 Bg4 18.a3 Bxf3 19.Bxf3 Nc2 20.Ra2 Nd4 21.Bd1 Nb5 22.Ba1 Nxa3 23.Rxa3 Rxd2 24.b4 Nd3 
25.Rxa5 Rxa5 26.bxa5 Bc5 27.Bb3 Nxf2 28.Kg2 h5 29.g4 Nxg4+ 30.Kg3 Rd3+ 31.Rf3 Rxf3+ 32.Kxf3 Nxh2+ 
33.Kg2 Ng4 34.Bc3 Kf8 35.e5 Ke7 36.Kf3 g6 37.Kf4 Ne3 38.Bd2 Nd5+ 39.Kf3 Bd4 40.Ke4 Bc3 
41.Bg5+ Ke6 42.Bc4 Bxe5 43.a6 bxa6 44.Bxa6 f5+ 45.Kf3 Bf6 46.Bc1 c5 0-1

Cekro-Van Mechelen seems like the most logical plan to me (ignoring the queen sortie with 7.Qe5+).  If white can successfully contest the center with e4, I think this is the way to go.  

Has GM Kosten covered this line?  It would interesting to see if he has comments on this line.  I think this plan for black is quite interesting.  

On a side note, I have noticed that often a good way to find a good line to play against an opening is to look at the games of the authors (or, more generally, specialists in the opening) who wrote repertoire books on the opening, and see where they have the most trouble in their own games.  Often this may indicate a weakness in their coverage of the line!  I imagine it takes some guts for an author to play the lines he recommends in his book!

   

what about the move 6. Nf3 Bc5 7. Qe5+! forcing the bishop to retreat.