IF you were forced by gunpoint to pick one, probably attributes. At least historically from what I have seen, people want the higher attributes so they can sink more into vitality. But a random one with 5% vs 10% XP, if the player specifically needs a 10% ASAP, maybe they can give 1fg extra. Problem is Annis are just not worth much anymore unless it has the really high dual stats of at least Attributes + Resists. Want to actually sell it for something? Then have a 19+/19+/10%, otherwise these are now worthless dime a dozen.
Last ladder I had about 15 to give away for free, I literally could not find anyone who wanted a random Anni. Go figure. So with all that conveluted answer I will resort to this:
depends on person or character
Pretty much the only real answer.