Well I had a TP-Link router and it seemed problematic at times and I didn't like the way TP-Link generally didn't provide an update to the routers firmware for over the last 2 years, which perhaps I was being over cautious about but when I look at security/performance fixes in other companies firmware either TP-Link are awesome at firmware and don't need to update it or aren't bothered.
I had planned for a while to replace it and I liked my previous ASUS routers and while being more expensive they tend to have some nice little features like AiProtection, not a complete security blanket by any means but something to complement other security I have as well as training my olds to minimise brain farts. The spec in terms of processor, memory, etc also seemed to be some of the best as well, again a result of the higher price no doubt and you could question if I'll use all of it but it does appear to of sped up the Asus interface at the very least
Ironically reading the article on this very site I realise that the current raft of 11ax routers use the draft spec and there are bound to be some things it won't include once it is fully certified, also there is no client out at the moment that does 11ax although this router is a keeper for probably 2+ years and with chips like the snapdragon 855 chip due in phones next year I would expect some 11ax devices to start appearing on my network within that 2+ year period.
As for the 8 ports well this is more down to future plans for when I move house to use more cables to attach switches in different rooms around areas where large groups of devices that can be cabled gather such as TVs, Consoles, PVR, computers and Sonos. I might also put up the odd camera as well which I can use with my Synology DS1815+ and the DS is the reason I decided that 802.3ad would be quite nice and yes I may well never actually take advantage of the full capability but generally it seems 802.3ad is standard on all the 7/8 port routers.
Possible options (Amazon UK Prices):
Asus RT-AC88U - £229.98
Asus GT-AC5300 - £339.00
Asus RT-AX88U - £299.99
Netgear R9000 - £387.00
Netgear XR700 - £449.99
I won't deny there was a slight pull towards the new and spangly but overall it had what I needed now and what I will need in the near future, will the AX88U have issues....sure will.