Smog-era Muscle: I'll have the Mustang. Unlike about 98% of car people, I actually like the looks of the Mustang II. And plus it's far rarer than the Nova, considering I've only seen 2 or 3 II's and I've seen countless late 70's Nova's.
NYC Taxis: My choice depends on what I would be using the car for. If I used it for what it was actually designed for (being a taxi) I'd have the Nissan NV200 because it has a ginormous interior that even I could fit in, and also when a normal person has the choice of going with either a Crown Vic or the Nissan, they're probably going to go with the Nissan because it looks more inviting, as well as having a far bigger interior. The Nissan will get better gas mileage, and their is no arguing against that. And lastly, it has a glass roof, which is just cool.
If I was using one of them as my normal cars, though, I'd get the Checker. It's a classic, and the others just....aren't.