I've not used an Asus card so hard for me to compare, but I've had my Z from release and find it to be a very good reliable card. Sound quality is great, with good speakers definitely a notch up from on-board.
My only issue is with Creative Labs driver releases being few and far between. Fortunately I've not really had any issues other than on the add reboot the card not being detected with Windows 8.1 which apparently is driver related.