Do you remember a few years back, when Enta were the first ISP to go for BT Wholesale WBC? It was utter chaos, with all sorts of capacity problems and unhappy customers. Which made the resellers unhappy as well.
That was when the ones we know of started looking at alternatives. UKFSN looked and seem to have done nothing practical. Vivaciti stayed with Enta for the "Family Allowance" packages but have continued to accumulate other options. ADSL24 shifted the whole of their Enta allowance customer base to what was then Murphx, on virtually identical packages, and are also continuing to arrange other options.
Both seem to me to have perfectly OK customer support and to genuinely try to get things right. As I said earlier, I think one or the other will be right, but wouldn't want to "plump" on someone else's behalf. If I were choosing between them myself I would probably toss a coin and be prepared to swap to the other after a couple of months if it didn't work out for me.
It's merely a question of how the backhaul capacity for each is for your location. In most cases I would expect both to be fine.
An important thing to me is not to use any ISP's email provision. See my
ISP-independent web/email page. Removes nearly all the hassle from migrations as you never need to change your email address again.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost.
Internet connection - Plusnet Value Fibre.
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.