The Sin7 is the rebranded S3. A lot of people really liked the S3, it never appealled to me. I have had a pair of S7s for three seasons and have probably over 100 days on them. I loved them at first. I now wish they were stiffer, had a straighter wider tail, not so much rocker at the tip, and were not quite so wide. I think I just described the Soul7. I have a pair of Soul7s that I just got this season. I demoed in calf deep slush last spring and I skied my new pair for a few runs this year and they were great, but I plan on not getting into them too much until we have a bit more snow.
I had a conversation with the Rossi rep last week. The new Super7 with the aircore tips is much lighter and more nimble than the previous Super7. The Soul7 is selling like crazy, but he told me that he thinks the new Super7 is probably the best powder ski option.
I'm thinking I will probably sell my S7s and maybe my E98s a bit later in this season.