I think they both left their impact on the sport. I don't get how any one who puts in the years they have can just be cast aside as any old competitor. Michelle was at the top of her sport for a decade. I can buy a competition here or there the judges "gave" her, but not for a decade. She did make her competitors better-those that beat her soundly HAD to bring a 3/3 and I can think of only one competition where Michelle was pretty clean that she lost (1998 Olympics). During Michelle's reign, 7 triples became the goal for the ladies, and Michelle put forth several 7 triple LPs, and a lot of clean 3/3s, but since they were "only" 3t/3t, people have to dismiss that as an impressive stat. Michelle did popularize the COE spiral, hands behind the back/lowered leg layback. She did a Y-spin on both legs. There have been a lot that Michelle brought to the ice that is being emulated by new skaters every year, to say she didn't revolutionize the sport is being petty.
Sasha took what Nicole did, what Karyn before her did-used her flexibility to highlight her programs. Sasha has great lines, amazing positions, pointed toes, can contort her body in inhumane positions. I did think when COP first came about, the creators had Sasha in mind while thinking up rules for spins and spirals. I am glad in recent years, those rules where ammended so skaters with less flexibility (Yu-Na, Kimmie) can achieve a level 4 spin/spiral without breaking themselves. Mirai, Caroline and others say they idolize Michelle, but I see Sasha's influence in them, which is why they can succeed under COP in regards to spins/spirlas-flexibility maxed.
I wish Sasha had challenged herself more. I think people see her flexibility, fast spinning and choose to ignore she landed one 3/3 in competition (albeight a very tough one) and never had a clean 7 triple program (save the fluff event). But I do feel she left her mark on the sport, and did help revolutionize the sport by popularizing being gumby-like, which helps under COP.