Both the JB4 N55 and COBB are great choices. It ultimately comes down to what you're looking to do. The JB4 is a piggy back where as the COBB is a flash tuner. The Cobb is much easier to install and to most, it is considered to be more user friendly. You also get free updates for life and all updates can be downloaded straight to your handheld unit from your PC/Mac. JB units will always require hardware upgrades which do cost more money (ie. JB4 stage 1 to stage 2 or JB3 to JB4).
Cobb N55 stage 1 Peak Gains
Aggressive: 11%HP / 25%TQ
Sport: 3%HP / 14%TQ
Cobb N55 stage 1 Max Gains
Aggressive: 18%HP / 26%TQ @3200
Sport: 10%HP / 14%TQ @3200
up to 60hp to the wheels (80hp crank) on a completely stock car or up to 100hp to the wheels (120hp crank) on a fully modified car