i don't know 14 well enough but a 14 priest is really good. they have a fear and so are actually quiet viable. the only down side is you lack a little haste that a 10 would have. doesn't matter though, you'll have a lot of fun on a 14 priest
I've played both for a good amount of time. I personally choose disc over shadow not only because of the in-combat regen, but because a lot of races have shadow resistance. I see it as an advantage to bust out more holy damage, which cannot be resisted.