I own a 2011 Mustang with the big V-6 and 300+ horsepower, etc. as my summer car. It is a 6-speed. It drives great, has all the modern safety features, is very comfortable, doesn’t rattle and gets over 25 mpg in mixed driving as well as it gets looks everywhere I go. I know the older cars are full of memories and panache, in fact I used to own a 1970 Buick GS Convertible 455. The problem is that they are death traps, have poor brakes, suck gas and emit lots of pollution, and are often in need of repairs to their old parts. I say get the car you can love and trust unless you fancy working on your car. If that is your “man” time, get the older one. It can be great fun and very satisfying to work on an old car. But if you’re like me and rather be on the golf course instead of in the garage, I recommend a used late-model that someone else ate the depreciation on as the preferred option.
One very nice thing about an early Mustang is that nearly every part is still available from aftermarket suppliers. If I were looking for another old car to drive, I’d be looking for one too. Be sure to pick one with NO rust. A really nice one can’t be had for cheap money, but one you can drive while you work on it probably can. Keep in mind that a good early Mustang will probably never be worth less than it is today. It gets my vote.
If you want to keep your Jeep Commander, commute a long way with good gas mileage and reliability and few repairs and drive a classic car, you need 3 cars.
One advantage of the older Mustangs is that a small tote tray of basic tools will handle just about any repair or maintenance problem that ever exists.
It wouldn’t be difficult to rig up a CEL on it just to mess with some minds; maybe with a hidden switch and turn signal flasher to get it blinking… 
@jr4488, stop confusing us with thoughtful comments.
Seriously, I agree with you about new vs. old visions of the same car. I would rather have the new on, too. I’m amazed when I see an old Corvette go for twice or more than the cost of a new one that will drive circles around the old one. The new one handles better, brakes better, is quicker, and gets better gas mileage.
Is the 3~4000 price tag you’re looking at the original purchase price, or the current asking price?
Lots of cars used to cost 3 or 4 grand, today, they’ve gone up in value a bit. In today’s money, that would likely buy you a rusty car that’s in need of restoration. Can you afford to be without a vehicle for the 3 or 4 weeks/months it might take to get 1 certain part that is out of stock, but needed to get your car running again?