Penny™ Viola (Viola x williamsii) seed cultivars are bred and produced by Syngenta Group.
Sorbet™ and Sorbet XP™ Viola (Viola x williamsii) seed cultivars are bred and produced by PanAmerican Seed, part of Ball Horticultural.
Both Ball Horticultural and Syngenta are huge International agricultural corporations.
Both companies also produce lines of Pansies (Viola x wittrockiana), but the plant pictured is a bedding Viola.
Both Penny™ and Sorbet™ have a wide variety of Viola colors and patterns. Each company has their own versions of most of the basic solid colors and blotch patterns as well as more unusual and complex patterns unique to each line. Some of the cultivar differences involve the number of weeks from germination to sale, and whether the cultivars are better adapted for early Fall-Winter sale or later Winter-Spring sale. In my climate it make smore sense to plant Viola in the Fall so I can enjoy them for six months or more.
I've grown many Penny and Sorbet/Sorbet XP viola, but I haven't done any common garden tests to truly compare them. Even if I did, my 'common garden' conditions would still be different than yours. I have noticed that some color forms are more vigorous and floriferous than others. For example Blue and blue blends like Delft Blue seem to grow and flower more than some other colors. This true regardless of which company produced the seed. Overall, I've been happy with both Penny™ and Sorbet™/Sorbet XP™.