I think Asus cards do sound better for music and films. I have Asus' cheapest card the DS in my HTPC, and for music it's sounds better than my X-Fi Xtreme Music. The difference is not huge, but it is there.
Creative won't open source EAX, not if they have their way. They will sell it on if they can, which they have done to Auzentech. If they do open source it, I will probably fall off my chair. EAX is their main advantage over Asus' Xonar range, once that's gone why buy a Creative card. EAX is clearly superior with Creative cards, so anyone thinking Xonar's will sound just as good with emulated EAX is just wishful. I am sure for the most part Xonar's do a decent enough job of emulation, but for a lot of gamers, decent is not good enough.
It's a pain in the rear that Creative can't get their backsides into gear when it comes to the software. If they were more reliable as far as the software goes, Creative cards would be a no brainer choice for gamers.