Here's what I'll say about Cook vs. Pettit. You can't make a bad choice here. I think Cook deserves every ounce of praise he gets, and likely deserves a statue when he retires. I'll start the funding campaign for it.
But Pettit did something Cook has never done. Never had to do, because Pettit already did it. Terry Pettit created a national powerhouse out of thin air. When he came to Nebraska in 1977 there was barely a varsity volleyball program. Prior to 1975, Nebraska didn't even sanction women's sports. Pat Sullivan was our first Volleyball coach, and created the program out of what was basically a club, going 81-23 in her two seasons. When Pettit took over in 1977, he quickly realized that he had next to no recruiting base in his own state. So Pettit not only trained his own team, he went around the state training high school coaches how to teach volleyball.
And he did it again the next year. And the year after that. And the year after that. He basically taught the state of Nebraska the sport of Volleyball. You can go to Chadron, Norfolk, Tecumseh, watch Class A, Class C1, Class D2 matches in this state and you'll see kids who know the sport, many of whom have legitimate aspirations of playing D1 volleyball in college. The Club scene in this state is crazy, and regularly produces top talent that competes & wins on a national level. That's entirely because Pettit created the knowledge of the sport, the passion, over decades.
I mean, Cook's record & winning percentage, conference titles & national championships speak for themselves. I wouldn't trade Cook for anyone - maybe not even Pettit in his prime. Cook may be the best volleyball coach of all time.
But that's the only reason you wouldn't put Pettit in there. Above Devaney. Above Pepin. Above Osborne.
Also, little addendum to that - the kids that go through these programs are students first. And every kid that went through Pettit's program in the 1970s earned a degree while she played. You put four years into Pettit's program, you graduated. Also, every kid from the 1980s. And the 1990s. In fact, every kid who's ever gone through this program, ever, has earned a degree.
No other sport can boast a 100% graduation rate. That continues with Cook, but it started with Pettit.