Dzeko is 1 year younger, quicker, better movement off the ball, slightly better skilled - in other words, he is a more complete player.
So I don't care about the money, it's not mine. I'd take Dzeko over Llorente.
But if you consider money, 15M for Llorente would be fair, and 25M for Dzeko would be realistic.
---------- Post added 09.08.2012 at 18:33 ----------
And yes, I doubt Athletic will ask less than 20M for Llorente. And Marotta will start offering stg around 12M, just guessing. This could go on and on. So if we can really get Dzeko for 25M, just do it.