It's pretty simple to get those answers. Just start reading the forum! Start with the manufacturer subforums.
You'll get plenty of "My Cobra is Better Than Your Cobra" opinions, but in the end you won't really find that any one of the majors is better than the others, just different.
If you're looking to purchase please refer to
427 Cobra Country--Ford AC Cobra replica manufacturers SUPER-SITE and remember they are for sale ads so they want to make their car look better than any of the others.
I strongly encourage a personal inspection of any car you purchase. The cars are quite small and cramped, and you should determine if your car "fits" before buying it. I found the difference between a Superformance and Shelby CSX was whether the steering wheel rubbed on my lap or not.
Good Luck!