Yes ive heard that too, also i understand what you mean. Both have good sound, but price is better on the blue flame.
Dont think you will get a bigger pipe unless its a special made item then it will be more money.
The std st170 is bigger than a normal 2.0 L focus so thats why the blue flame is not any bigger, im sure it will sound good and if you fit a sports cat or evan decat pipe then ya get better performance too.