Noooo! That's not how you play it! 

1. Nf3 b6 2. c4 Bb7 3. g3 Bxf3 4. exf3 c5 5. d4! cxd4?! 6. Qxd4 is better for white as white's bishop pair tends to get very powerful, much better is to keep control over the d4 square with 5...Nc6! when you will always have a potential outpost on the d4 square for your knight.

Of course it's very important that white in fact playes 5. d4 otherwise black will probably even have an advantage because of hes grip on the d4 square.

A tip for english opening players is to play the move-order 1. c4 b6 2. Nf3 Bb7 3. Nc3! e6 4. g3 when the plan of playing Bxf3 is much less effective because black has committed to e6.

Because if we look at the following variation:

But imagine the same variation is the extra moves Nc3 and e6 put in...

Conzipe, is this 5...Nc6! your idea or you see it somewhere?

 Does it really matter? ^^

Actually this is not an idea I came up with myself, I first saw this idea in my database and I thought it looked like the best and most principled move even though it haven't been played as much as cxd4. And these thought was confirmed when I decided to get some resources on the english defence, notably Daniel King's book about the opening and an old video by brittish GM Plaskett on the english defense they both seem to share the same thoughts about the position.

I dont have the GM King's book and this 5...cxd4 6.Qxd4 Nc6 or 6...e6 is the GM Bauers' suggestion in his recent book play 1...b6!?  (I have it).  He consider 5...cxd4 slightly better than 5...Nc6!? but I think you are right here - White bishops might become very powerful after 5...cxd4 etc. so 5...Nc6!? should be better. In fact after 5...Nc6 6. d5 Nd4 7. Be3 GM Bauer consider only 7...Nf5 but not 7...e5!?, which looks stronger!   

Thx :))))))

I just looked a bit more carefully at my databases. 5...cxd4 is played a bit more frequently (and with a reasonable success by Black)  than 5...Nc6!?  However, the obtained positions are quite sharp and unclear and White should be somehow better.