Is anybody growing both of these plants? How are they different?

I find that the photos in COTW for both MBV and CDB look very similar.

The two photos on COTW look like Chalk Hill's photo of MBV. CDB looks different at Chalk Hill's.

I have a 10-year old clematis which I thought was MBV. Just to be sure, I purchased a CDB -- that was 4 years ago. Both are blooming right now and they look like the COTW photos for MBV.

More confusing is that they bloom here from late May/early June till August/September -- much earlier than described at COTW.

Not really complaining. Just confused.

They have been really good plants to me. Vigorous and wilt-free. Really profuse bloomers, too. And so easy to propagate by layering!

TIA!