Personally I'm sticking with Zen as I consider them the best short of aa.net.uk which are WAY too expensive for my usage.
Out of my two lines, I see more packet loss issues on Plusnet, so much so I had to move my VPN clients over to Zen. Not sure why, other people have said they have no issues.
Ultimately after looking at some of their videos, I have more faith that Zen are investing in their network and they claim to maintain a zero contention network. I don't like how the big ISPs can have websites blocked by court orders, I did years ago experience a whole IP range incorrectly blocked on Plusnet because they made a mistake updating their blocklist. I just feel more comfortable knowing that can't happen because Zen do not block anything.
Granted that could change, if Zen are ever considered big enough an ISP then the courts could demand they implement a blocklist, but we will cross that bridge when we come to it.