it say go with the bullitt. yes i own one. and that makes me a little bias, but ill give you my reasons why.
Looks: IMO i like the sleek look of the bullitt over the others. The cobra looks is serious, and is bad ass. The Mach looks old school, and shows heritage. The bullitt is sleek, no wing, unique color (if green), plus was the first of the limited edition cars (besides 35th aniv.) that were made, and there are only about 5600.
Interior: Bullitt and Mach interiors are very similar. The seats in the Mach and Bullitt are the same in terms of bolster. so its a tie. Cobra interior is also nice, and the 2 tone seats are sweet. Your choice as to which wins this cat.
Performance/power:The Mach 1 is the fastest. hands down. The live axle, and the lower trq lets this thing pull away from the cobra down low. Up top its a tie between the Mach 1 and the Cobra. The bullitt will pull on a cobra down low. This is not a lie. Ive raced pre 2003 cobras, and the bullitt can pull on a cobra off the line. The bullitt, only have a 2v head, lacks hp up top compared to the cobra. So, once off the line for a distance, expect the cobra to pull on the bullitt. The live axle, and the more trq downlow gives the bullitt a slight advantage on stop light brawls over the cobra, but gets pulled by the mach1.
So, IMO if you want pure performance, go with the Mach1. If you want handling and power off the line, go with the Bullitt. If you want up top power, and a smooth ride over bumps, go with a cobra. The reason that i pick the bullitt is that its very good in all catagories. It has good power, a sleek look, is unique, its the first of the limited editon models, handles very well, is lower, and has an intake that is also unique (stock) to mustang.
thats my .02$. no flames please..lol
Mike