Ok, final answer:
If the goal is variety, definitely go for vials, wherever you get them. They're cheaper.
If the goal is a full application and you don't care about trying as many scents as possible with your funds, go for the larger spray decants.
Either way, I would go with Perfumed Court, as they have just about the best selection. And if TPC for some reason doesn't have something you want, LuckyScent probably has it as a back up.