My 2p
CyB is lovely, it’s rocky as bawls rather than fast and flowy (as a rule, there’s a lot of trail there). I know a few points off because the centre isn’t really where the trails are so you either ride a little loop over the road, or a little loop up the hill, so on a busy day it’s really busy at the start and end.
Marin was mind-numbingly boring for me, a pain in the arse to get to, seventy million miles of featureless fireroad, nice enough single track but nothing unique enough to travel for and a nice final descent. It’s also deep in Kendal Mint country so MTBers are about a welcome as a dose of syphilis by the summer crowd in the local cafes (there’s no centre as such).
Llandegla is a Theme Park, it’s the least ‘natural’ TC I know, but I love every bermed, whooped, table topped bit of it. The cafe also sells AMAZING burgers. It’s a 4hr drive for me, but I go about twice a year.
Nant Y Arian is deep in the ‘desert of Wales’ aka, the middle bit – it’s 2 hours from Chester, The Summit trail is awesome, like Llandelga, whilst it’s sold as having 3 trails, it’s more like 1 with extra bits you can add on for greater length, I haven’t tried Syfydrin (the Black one) but I’m told it’s old-school Black, I.E. longer than rather than more technical and it’s The Summit with 18k of easy-ish trail on the back end.