USC had a good team, but Reggie Bush was a special talent. He had elite speed and his open field moves were very good. Bush was never a good inside runner though, even at USC. He had no power. LenDale White would do a lot of the dirty work for that USC team because Bush wasn't cut out for it. Bush still had a good NFL/FF career though. Even when his YPC was bad, he was often startable in PPR leagues because he would catch passes.
McCaffrey isn't as fast as Bush was, but I think he's a much better interior runner. He's not going to be the 350+ touch bellcow like a LeVeon Bell or Ezekiel Elliott might, but versatile mismatch weapons have been big in the NFL for the past several years and McCaffrey is a guy who opens up a lot of possibilities. He can be like a better version of Danny Woodhead, racking up receptions and supplementing it with some rushing yards and TDs. I think he's going to be pretty good in PPR right away, just as Bush was.