Which do I plump for? Going to build it up with rigid carbon forks. Anyone ridden both?

Only ridden the Simple. Lovely bike, in 853 for extra points. But I didn't get on with the slotted dropouts. Be interesting to know how good the Sanderson EBB is.
Also, Cotic is designed for 130mm forks, the Sanderson for 100mm, so I guess the Sanderson will probably work better with the rigid forks in that respect.

I used 440mm long carbon rigid forks on a Cotic for 2 years, they were ace. Wouldn't go any shorter though.

The Sanderson EBB is excellent, its a different design to most others out there, but its been pretty much flawless in the 12 months I've been using it – no creaking or slipping. Can't comment on rigid forks, but I've happily run it with both 100 and 120mm forks.

Note, a medium Sanderson acutally weighs 5lb 6oz, about a lb more than the Simple.

Sanderson is lovely to look at but was rather too 'solid' for my liking, and I couldn't get their ebb to lock out properly.

Cotic would be my choice.