I'd probably say D7800 but I've never used it. I had an EdgeRouter (by Ubiquiti), although it doesn't come with a modem built-in, but they make good and reliable products in my opinion. The only reason I don't use the EdgeRouter now is because I have a Firebrick 2900 from AAISP for line bonding and as my main router now.
Prior to the EdgeRouter I had a DrayTek 2860Vac and Fritz!Box 7490 (both come with modems built-in), I found them both reliable. As for ASUS, they messed up with the DSL-AC68U and to this day still haven't resolved the reliability issues it has with DSL connections, I'm personally avoiding future ASUS modem/modem+router products (standalone routers are generally fine).
Edited by Ixel (Fri 11-May-18 19:47:01)