It's a tough one to comment on as I could live happily with either of them. They are very different sounding speakers of course. The bass especially is SO different in the Diesis OB speakers vs. the A5/sealed cabinet. Both speakers sound VERY OPEN.
The A5's are $25K and the CM's are $60K (retail). There would be those that would take the A5's over the CM, but then some would take the CMs over the A5s. The fact that the A5 is $25K competes with the $60K CM is saying something about the A5s value.
I love the Diesis speakers for all kinds of reasons. BUT I routinely tell people that the A5's compete with any other speakers that I have in my possession. It comes down to personal preference, but the A5s for me are a real over achiever.