I have stayed in a forward penthouse and aft penthouse on the Jewel to Alaska, If you don't mind the wind even on nice days the front is the way to go now if it's raining you're probably not going to stay out on the balcony very long. The aft on the other hand is very seldom windy and the balcony is always usable in my opinion, but slow sailing into port or a glacier there's nothing like that forward WOW factor!
Either way you'll love Alaska!