Welcome to the forum from Claremore, Oklahoma!
Your question is an age old question, there has been many, many posts here concerning that very same question. Do a search on the forum & you'll be drowning in answers.
All the manufacturers you mentioned offer good kits/cars. Some manufacturers offer kits, some offer rollers and some a combination of both.
I have an RUCC kit from here in Oklahoma but RUCC stopped making kits some time ago. I built mine and I love it, great handling and quality workmanship.
Research, research, research is what it's all about when considering which kit/car to buy. Here are just a few things to consider:
1. Go to local car shows to check out any Cobra's there & talk to the owners.
2. Come out to the Tulsa area sometime, there's quite a few out here. Most people will take you for a spin and let you try it on for size so to speak.
3. Go to the manufacturers facility for a tour.
4. Consider your budget - most times it's cheaper to build it yourself.
I wanted to build my own Cobra, wanted the feeling of accomplishment that goes with it & I also wanted a "one of a kind" Cobra.
You know your mechanical skill level, of course thats a big factor in buying one already built or building your own.
Again, thorough research is the key to a pleasant entrance into the Cobra world.
PM me if you're ever planning to be in the Tulsa area.
Good luck,
Randy