I'll go for older Elvis every time - he developed a real maturity in both his voice and musicality (yes, I'm using that term entirely non-ironically) that simply wasn't there in his younger incarnations.
I think Elvis could sing a shopping list and make someone cry. Sometimes when I'm trying to decide how to phrase something, I'll "play it like Elvis" to force myself to make a musical statement.
By the way, I have NEVER heard bass trombone playing like that on "Aloha From Hawaii" - I strongly suggest that it should be in any low brass player's collection.
Jeff "King" Miller (heh, heh, that really is my middle name!)