the 86u is defo better and I wanted it myself when I was router hunting, I just didn't have the $$$ at the time. Technically it has faster wifi (not that you'll use it) and the wan to lan throughput is an extra 100mbits (>900) but you won't be using that either. The wifi is great and I have no problems getting max wan connection speed on my ac capable devices which is ~350mbits.
One other thing you can think of though if you have got cables running to other rooms of the house as roughbeast has already suggested is putting a wireless router in there. Asus routers are awesome and have different modes you can use them in and you can specifically set to them serve as a wireless access point and use AI Mesh to create a mesh wifi network to work in conjunction with another Asus router. If I was you I would get the AC68u and have it on one side of the house (upstairs/downstairs) as your main router and get
this to use as a wireless access point and have it on the other side of the house upstairs/downstairs.