Neither have blooms the size of Selfridges, a relatively healthy 80s yellow HT by the same breeder family. They are both upright, and both have informal form. They both have special resistances.

Winter Sun is closer to cream, and Sunny Sky does not hold onto its medium yellow for very long. Winter Sun has more elegant peals and foliage, and Sunny Sky has more petals and sandpaper-like foliage. Sunny Sky can be taller than Winter Sun. SS resists downy and canker, and I am unsure if WS does. Have not tested it for that. They both have above average vigor, especially for their class. Although they would fit better with grandiflora class by bloom size along, Sunny Sky can throw classic candelabras grandifloras can be known for. However, SS is very, very prickly, and WS is less so.

I think weekend warriors would be better off with Winter Sun. The shape and height are better for the basic landscape.

However, if I had to get WS, I'd get Sunshine Daydream. It has a lot of personality. If I had to get Sunny Sky, I would get Gold Struck. It is much smoother for roughly the same color category classic yellow going lighter) and informal bloom form. I would not get either SS or WS. There is simply better competition out there, and since there is really no outstanding saturated deep yellow HTs out there, mid to lighter variants should be outstanding. SS and WS simply do not break the mold, except for introducing new blood to the yellow lines. But so do the comparators I mentioned.