I am about to get a new phone and am wondering if there are any downsides to simply using my old S8+ (which I believe is a cat16 LTE) for my home broadband rather than getting a full blown 4g router. I believe I can simply tether my phone to my Asus AC86U (merlin) to provide the wan access to the asus via usb, all my devices connect to the asus so effectively my setup is identical except the wan comes from the usb instead of the old FTTC phone line.
What I am not sure about is if there are any down sides to this setup vs using a 4g router? I can get maybe £120 for the phone if I trade it in, a 4g router is going to cost more than that (a lot more if I get a cat16 one vs the usual cat6 most seem to be). So it will work out cheaper provided there are no drawbacks to doing this. It also means I am not buying a 4g router which will be obsolete as soon as I get 5g here (which might be soon as there is a fair bit of coverage around me, just not at this location yet).
I get 50-55mb at most via my FTTC with an 8ms ping, I can get 120-140mb over 4g on this phone with a 15ms ping (seems pretty consistent in all my tests day and night). The FTTC is costing £50/month including a phone line which I don't need. I can get the sim cheaper than that and more than double my speeds at the same time and it seems all I lose is 7ms of ping.