I've tried the oil based spray paints, and I've used acrylics. Using an oil based paint is stronger coat for coat than acrylics, but my opinion is that acrylics give it a more realistic and softer coat. There's also an even trade to curing the paint. Oil-based paint can sometimes take up to 3 days (I've seen it) and during that time, dust can attach. Also, if you need to do more than one coat, you could be looking at a long week. Acrylics, though, usually dry within 2-12 hours. But like you said, they need a primer, and mostly an overcoat, which is good to give them anyways. A nice dull or matte finish after applying decals will always make a valk look more realistic as well as protect it.
If you're talking about airbrushing, I'd ONLY use acrylic. Tamiya is a great paint. It bonds well with oil and water based paint.