Generally speaking, the farther the form of a dahlia flower departs from the ancestral form, the more likely it is to have problems in our climate. When I look at the catalogs, I'm drawn to the anemone-flowered sorts. The ones I've tried produce mostly malformed flowers. 'Boogie Woogie', shown above at the top of the series of images, is an anemone-flowered sort.
The next one is 'Esther', a collarette sort. So far this year, most of the flowers this one has produced have been missing one petal.
Next is 'Sandra': I have no complaints here.
The last one is 'Gallery Art Deco': so far, the flowers of this one have been hidden down in the foliage.
I planted twelve sorts this year, so look for eight more in the weeks ahead.