I find it varies from character to character. In general, I prefer Encounter powers - anything I can rely on getting regular use out of. On the other hand, my Swordmage has stocked up heavily on Daily stances that last the entire combat.
I suppose I'd say that I go for powers that last an appropriate amount for their availability. I generally won't go for a Daily Utility that only has a one-round effect, but I'll go for one that helps for an entire combat. Whereas I'm fine with an Encounter Utility that just gives me one action or brief effect, since I can rely on using it in every combat.
At Wills are rare enough that I can't really say either way - if they are fitting for a character, I'll go for them, but they tend to be weak enough (to make up for their constant availability) that I only see them in use for very specific builds or concepts.
I suppose I'd say that I go for powers that last an appropriate amount for their availability. I generally won't go for a Daily Utility that only has a one-round effect, but I'll go for one that helps for an entire combat. Whereas I'm fine with an Encounter Utility that just gives me one action or brief effect, since I can rely on using it in every combat.
At Wills are rare enough that I can't really say either way - if they are fitting for a character, I'll go for them, but they tend to be weak enough (to make up for their constant availability) that I only see them in use for very specific builds or concepts.