Yeah they have room for insane courses at El Toro. It took 20+ minutes to walk the course once! Those were some of the best courses I've ever driven. You ought to think about doing an event down there, the site is "only" 4 hours from my house.
Which Miata? The NC MX-5 is actually really difficult in a way. There's no feedback through the steering (I'm really surprised at this) and there's basically no neutral balance in the car. At least we haven't found it yet. It likes to understeer but it's also loose at times so I'm constantly searching for either front or rear grip in a corner. But it has surprisingly decent power and goes fast anyway. It runs 245 Hoosiers all around.
The 1995 turbo Miata is more fun, but then it should be with 240rwhp at 2300lbs. :) The older Miatas fit my driving style really well. They don't understeer much and when they do, it's easy to fix, even with a stock engine. They have good steering feel too for a power assisted rack.
Neither of them are very much like the MR2s. MR2s are pretty unique in the way they drive. Generally Miatas are easier to get fast times from. They're not as challenging as MR2s at the absolute limit. Right now Mazda has great support for the amateur racer so it's been good for me to run Mazdas the last couple years.