Apologies for the unintended plug; I’m trying to explain why AA is right for me because the many answers may well not be obvious unless you have dug deeply into AA’s website.
It’s also the services AA provides: DNS that you can manage yourself, CQM graphing, ability to run lines tests and change settings such as SNRM, free IPv4 and IPv6 blocks, line up/down alerts, IP bonding, support for failover to 4G, excellent email and probably a lot more if I put my mind to it. It’s that richness that made me chose them over Zen, not support. It is superb though having a one-stop shop for blame: no buck-passing, I’m talking to the people who designed my Firebrick itself, so any problems and I can get them fixed.
A lot of people think it’s all about support but for me it’s not just that. Some of my lines have become much less reliable since the beginning of 2020, for reasons unknown. The ‘hollow in SNRM-vs-tones graph’ phenomenon keeps coming back.
Some of us like things such as having control, being able to initiate things without having to pester the ISP, having comprehensive detailed stats. I’m one such and there are probably others among us who think that way.