I would chose the Caradonna by far. My others are slow in coming along and the Caradonna just jumped right out there and it's younger!! It has a lovely dark purple stem that is a gorgeous contrast to the purple flower.

I agree with Paulette about Caradonna , same color flower as May Night but better foliage by far! I also love the color of E. Friesland. The same mellow lavendar blue as Scabiosa Butterfly Blue & Russian Sage.

May Night's blooms are a rich, deep color. Very striking and long lasting in my garden. By comparison, my East Friesland's blooms are somewhat lighter in color, but still very nice. The foliage on East Friesland is beautiful, and less "wild" looking. I love and need them both ... you can definitely tell them apart from one another.

Randy

I love Caradonna the most. Planted last year, it is up more than 12 inches already here at zone 7 and with Flower buds.

My Blue Hill is only 4", while my May Night and Purple Rain did not come back :(

East Friesland has lighter-colored flowers than May Night and Caradonna, but it flops horribly after the first rain, post-flowering. And it does NOT recover. I've read that if you shear it back, it will recover; I've not tried this, as 1) I'm not into maintenance for zero reward as 2) this solution is only as good as the length until the first rain post SECOND flowering!

This year, I've bought one each of the other two. I've read the bloom color is the same, but on my plants, Caradonna is darker, deeper red-violet purple, and May Night is a medium-dark, blue-ish purple. I've read Caradonna and May Night both purportedly flop less than E. Friesland (it's chief complaint, from my research). For more on the purported foliage differences, etc., I highly recommend this link:

Here is a link that might be useful: David Beaulieu, About.com writer - Caradonna vs. May Night Salvia