Look at this comparison / thread:
http://www.e90post.com/forums/showthread.php?t=374508
JB4 has the most N54 cars in the 11second range. Cobb is not faster than a JB4. It may be more convenient yes because you use a hand held flash tuner but that is it.
Also Cobb hasn't even come out with anything for the N55 so it shows how far behind they truly are.