I think you need to get an AirPort Extreme or your asus RT-N56U might turn into a pumpkin
No seriously...
I am not up on the asus so I cannot compare, although I have always thought they produce the best routers.
But in favour for the AE. I have used one for a few years. If you run all Mac/Apple, then it works seamlessly. You can add on AirPort Expresses in any corners of your house to create a complete network and that only take 30 seconds to do.
The AE allows you to plug a USB hub into the back and run multiple USB disks that appear in Finder just like that.
You can run Time Machine onto them as well. I have four Macs that each backup to a separate drive on the AE so when I need to recover I can do it over the network (even in recovery drive) or via the USB direct. It works well with portables like my MacBook Airs because they seamlessly backup where ever they are. This is obviously similar to a NAS but it works seamlessly across Apple products and finder in OSX
The AE has options in the Server App if you use that (i don't)
The AE is controlled via an OSX App that shows all your expresses as well. You can also run that App in iOS from say your iPad.
The Airport Expresses (if you run one or more) have AirPlay as well.
All-in-all I have found it to be bullet proof and in particular with the dual band with OSX.
Whether it is better than the Asus I don't know, but the AE is definitely a solid router from my experience.