Your FIRST car, and you're trying to decide between a MUSTANG and an SUV? Are you sure you're alive?
I'd have assumed the Mustang (especially the brand new Retro design) would be the answer. It wouldn't be MY answer, but thot it'd be yours.
You didn't mention your age, because that sometimes has an effect upon what you'd like to drive or like to be seen in.
(sometimes equally important)
The smaller SUV's are usually quite nice to drive, smaller so they're more nimble in traffic, and won't guzzle gas like their bigger bro's. You also will sit up higher, able to see traffic ahead of you much easier, which is very helpful sometimes to avoid problems coming up.
Toyota Rav4, the Hyundai Sante Fe or Tuscon (forget which is smaller one), seem to be very popular. But the Toyota is proven by ten years or more.
You also didn't mention whether you're talking brand new or used vehicles. But either way, the Toyota is one of the best reliable.