+ 1 to the last post about multiple AP's.

For example it ultimately depends on your requirements. 
If you live in a small (2 bedroom sized house) for instance then an all in one type router will probably be sufficient and a good option.
If you live in an apartment building then everyone will have wifi and it will be super noisy. So a 5Ghz Dual band solution might be better.

If you live in a massive house then having a router and multiple access points will most probably be better. Also more people would live in a larger place, so would therefore have more wifi devices so having more ap's would be beneficial.

I wouldn't get strung up on the brand. This usually doesn't mean much. I have had terrible linksys units before and some great ones, same with ASUS. 

One of the biggest problems with all in one units is more often than not where the ONT or master filter is installed in your place is normally NOT the best place to put a wireless access point. Which is why having a separate router and wireless access point or points is probably a better solution. 

I am using ubquiti unifi 2.4 ghz AP and i get about 20mbit everywhere in the house. Which is fine for me because my internet speed is about that and if i want to copy large files between computers I use a ethernet cable. Its placed on the ceiling in the middle of my house and I have never had a problem with signal on any of my devices. I am using a router which is not WIFI to do my internet in conjunction with a  vdsl  modem to do the bridge. 

Currently building a new house and will be able to move this gear and use it in the larger place. with the hope i will get ufb (2019) :(.. But ubquiti are releasing new ap range as richms mentioned and I also heard the xclaim access points are great. 

 

FWIW I had a fritz box all in one unit and although it was not a bad unit, from where it was placed the wifi was not good at one end of the house. I also had loads of problems with the VoIP on it so I decided to use a pap2t and I had all sorts of problems so I sold it.