I've owned 4 MR2s. I owned a '91 n/a, which I really liked. But to me, it was more of a highway cruiser (I know the turbo is a whole different animal). I've owned 3 MK1s. My current is an '85, I took it to work today in fact. They are true gocarts, but the oversteer can catch you by surprise. It's amazing how fast it can go around. Lots of fun during autox, but I'm nervous about taking it on the open track (not to mention it's got 112hp, so I'll get run over).
As for the best Cobra, you're going to find that's a lot like asking Ford vs. Chevy or small block vs. big block. I'd dare say that none of the major manufacturers makes a "bad" car. The quality greatly depends on the parts you put in and the skill of the builder. You can get a "turnkey minus" car, which is complete less motor/trans. Superformance is among the larger of these, as well as Backdraft. You can have one built for you by any one of dozens of professional builders. Each one has it's own strong points, and I'll be the first to say there are probably better authorities on the specifics of
each manufacturer out there. I own an FFR, and absolutely love the car. Very inexpensive, open track and race proven chassis, very light weight, easy to gets parts, great owners group. But look around at all the ones you can.
Steve