Inimitable is a bit difficult to grow. Being EVR, it sometimes suffer from a hard Winter, and is susceptible to late Spring freezes. However, when it grows/blooms good--it is Great! It will then make Huge flowers that are a site to behold.
Green Mystique has great color and in full sun turns quite white in the afternoon yet retains great substance.
Great White is the best white to breed with because it clarifies the color of everything it mates with. Only problem is it is a finicky breeder that can be hard to get seed from. The color is very white. Only White Crinoline is whiter, but Great White has much better substance.
Michael Miller is really a good one that checks almost all the boxes, but tends to have a bit smaller flowers for my taste.
My all-time favorite Stamile white is: Victorian Lace. Here in USDA Zone 7a/b it grows really well and BIG. I lost my first one year three from a very hard Winter that gave us TWO single digit nights. Immediately bought another that Spring and have had No problems since. That was ten years ago.
If you can find it, Jack Bilson is a white bred from Stamile whites that is another great flower that is quite hardy here.
Inimitable
Great White
Green Mystique
Michael Miller
Victorian Lace
Jack Bilson
