I'd jump into an F-Type in a heartbeat, a nice white V8 coupe just drove past my office, shame they're still 80k... Better start saving
I'd drive them both before purchase, but i'd be expecting to want the V8. Depends on the depreciation and what else comes out in that time! Personally i feel like the 30-40k price point is pretty weak and bare at the moment, you're looking at 60+ for something really special (imo).
If I were going for an American muscle car it would be the Challenger, looks meaner and more exclusive than the Mustang! Although the Mustang will have the ecoboost option