I would be happy to chip in with my thoughts, but could you tell which type of Interlux paint you would be rolling with? They make many different paints.
I can say that in general, a two-part paint will give you a harder, more durable finish. Another difference is the shine. They will all shine at first, but the two-part LPUs can shine amazingly for 20+ years. They are actually more of a "coating" than a paint in that there is a two-part chemical process happening with them.
For myself, if I were going to the trouble to paint my egg (because, after all, 90% of the work is in the preparation, and that is the same no matter what paint you use), I would probably (have someone else because I don't have the experience or the air-supplied respirator necessary) use a two-part product.
I don't know as much about the typical Imron paint (and they may make different formulations, I'm not sure), but as I understand it, they are an acrylic polyurethane. It may be slightly less challenging to apply, and I believe it is buffable and perhaps easier to repair.
The "classic" Awlgrip and the like I'm more familiar with. They are a polyester polyurethane. They are very hard and shiny. Less buffable than the acrylic LPU, but on the other hand they don't usually need it. They are very hard and very shiny. Perhaps a bit more challenging to apply then the acrylics (but I'm not actually a painter!)
That said, the Tremclad-type enamel jobs are interesting; I can't speak to how they hold up over time. If I had to paint an egg on a very tight budget, and if I had plenty of time and liked to putter with paint, I might try it. (In reality I would probably save up until I could afford a two-part paint job, but that's just me, and the enamel is intriguing.)
But it's all just a tiny little step you do at the end of a lot of preparation