Anywhere except Moray! (See other post).
Seriously, all the Stanes are good with GT a clear winner and the best UK trail centre. Although Afan is now a close second and better than CyB. Absolutely loved Golspie - miles from anywhere but well worth it. And Laggan too.
The English centres are poor in comparison - Dalby, Grizedale and OK but nothing like as good as the Stanes or Wales.