I'm not sure though that a straight across comparison of the MB Ti frame and the Helix frame is realistic. Comparing the Cooper to the MB might be a more fair comparison. I only say this because the Helix is designed to ride stiffer.
I know you're looking for people that have ridden both, but I like my MB LeC Ti. I would really love to read the opinions of people who've ridden/owned both the MB and the Lynskey Cooper though.