If you checkout a few posts you'll find that probably nearly every manufacturer is represented by an owner on this site. Everyone (including me) of them will (hopefully) tell you why the one they chose is the "best."
I chose ERA because I felt their car best satisfied what I was looking for.
I know of several owners who use their car for a daily driver. They tend to be loud, both due to exhaust and wind noise, and quite often you can smell the exhaust while driving/riding in them. Ironically enough, many of the owners that I know own a cobra rep for street driving and another car, such as modified mustang or miata, for track events. One guy has two cobras, one for street and another for track. In my limited experience gas mileage can range anywhere from 5mpg to 21 mpg.
If you can find a used one that has what you want in it, you will probably get the lowest cost going that route. Check out cobracountry.com, there are always several listings representing many of the manufacturers for sale on that site. Of course, as with any "used" car purchase "caveat emptor." If possible check it out before buying it. If it is too far for you to check out personally, you can probably find somebody on this site who is local to the car who would volunteer to take a look at the car for you.
The closest you can probably get to "instant gratification," that you'll get in a new car would be Superformance as they manufacture theirs in almost an assembly line manner in South Africa. They have dealers throughout the US and make an excellent car. There is a post elsewhere on the site that Kirkham, thought by many to be one of if not the best replica out there, is having a sale and that would be worth checking out. Lonestar also has an excellent reputation. I don't think that you could go wrong with them either.
In the end it just depends on who meets your desires the best. If you decide to buy used, just remember that the quality of any of these cars depends almost entirely on the competence and quality of the builder.