I wouldn't have the tools or the mechanical knowledge I do (which is limited to mechanical, electrical is still voodoo to me) if not for my Toyotas. First being an old Corolla, and my 3 Supras over the years. ALL Supras will need work at some point, this is generally a fact.
All depends on the driver and the stang's setup. I've embarrassed many a Mustang over the years, no big deal. That said, stock for stock, you'll lose. BUT... your car will always be classy, comfortable, and probably be worth more in the long run if you take care of it. Put it this way: Mustang might be faster, but I'm sure Ford has popped out more Mustangs in the last week than Toyota EVER produced the Supras...
VERY good advice here. I will say this: I'm *still* in debt over a car I bought on impulse, and this was from 4 years ago...
All that said, my recommendation is still Miata. Girly looking is about the worst anyone can say about them. Bang for the buck, you'll have a hard time finding a car that will be as fun. Not to mention, if you have any canyon roads nearby, once you learn to drive one quickly, not many things will be able to keep up in the twisties.