The ASUS RT-AC66U features a wireless Media Bridge mode which allows one to create a high throughput 802.11ac wireless link between two RT-AC66U. So you can link up 2 locations wirelessly through the high speed 802.11ac.
So if you are going down to the nearest store and don’t know what to pick up, my advice will be getting the ASUS RT-N66U if you are tight on budget. However, if you need to link up your multimedia set up at home, then getting the ASUS RT-AC66U will be a wiser choice as 802.11ac is supposed to perform better than 802.11n on the 5.0GHz spectrum. (Source