I'm undecided. I need a big ride so either will work. The Pickwick is a lot closer but I could turn the Tan Hills one into a bit of a holiday and it's also different scenery, but there's 8hrs of driving to/from involved.
Seeing your crack was one of the many highlights :p
I'm told Mr Pickwicks is similar to BCM but with steeper climbs so if your looking for variation Tan Hills is probably a better bet. You could also further test your sleeping kit?
I'm riding Mr Pickwick in search of dragons and legends 600km on the June 11th
BTW I'm the Bristol rider you had a chat with at Menai and briefly at Kings.