I went with powder, Im picking it up from JRK tonight. So I cant tell you how it performs, but Id suggest powder just because it is known to be more durable. Thats why I chose it. As for price, like squadra said, it depends. The powder I used for my frame/swing arm, joe and sean said it was best with a clear coat, so obv thats gonna cost a bit more. Also there were some really cool powders that he had swatches of, but it would have cost considerably more because he would have had to special order them and the powder itself costs more.
Also Id look to have someone that deals with cars/motorcycles a decent amount do your powder work. There are other shops that do it in the chicago area, but their main business is doing lawn furniture and shelving and whatever. A guy that deals with bikes and cars a lot will not forget to tape off/plug mating surfaces and whatnot. Also I feel they generally will have a higher standard for their finishes, instead of some guy who is used to laying powder on street sign poles or whatever.