Downvote for downvoting due to elitism. Especially when the OP is on FTTP or G.fast so options are limited anyway.
I used to think the same as you did. I'd never go with a big ISP. But circumstances change and I did.
My zen connection had a weird performance issue that was ridiculously hard to get fixed (appeared to be a zen problem and they were difficult to engage - so much for customer service). One of the side effects of the fix was that I had to turn off IPv6 to be moved to another gateway.
My BT connection is both flawless in performance and in V6 usability. I don't look forwards to when it breaks, but it's all good for now. I don't have a static IP now but this isn't the end of the world.
It's no longer the days where the big ISPs imposed stealth caps, traffic shaping and nonsense like phorm. I'm not about to move to A&A and get a data cap just so I can get support over IRC or similar gimmicks.