Mustang and Black Ice plum comparison

mustang vs black ice. two western sandcherry hybrid plums, mustang is a mix with american wild plum, and black ice is crossed with japanese plum (P. salicina). mustang is very similar to Sapa and Sapalta , the result of decades of breeding into western sandcherry by Hansen - the large sand cherries in it's parentage are maybe lost but these chums or cherry plums live on. Black ice in this photo isn't fully ripe on Aug 16, I left a few on the tree to pick next week. my impression of mustang, it's better than I remember - sweet and excellent plum flavour, the skin is just slightly tart but it wouldn't slow me down from eating them fresh. Both of these plums are exciting because they fruit early, the year after they're grafted - and with the sand cherry parentage they have a strong rooting ability from cuttings. with mustang (Prunus 'Jeffchum') we propagate them for rootstocks, and our collection of related chums like Manor, Dura, New Oka, Compass, Bei Tang, Epsilon, these are all bushes at the nursery that are stock for new plants every june, and aspirationally I would like to try and create some new ones. One more note about black ice, it seems zone 3 hardy. Our grafts last year got hit with some -40, it wasn't a mild winter - and they pulled through fine. they deer got one this week, but that just tells me to graft higher and use cages: