Cory's OK for a change of pace, but...
For starters, Cathe's cueing and form pointers are right on the money. Cory has difficulty keeping the beat, and she definitely does fewer reps. She does the reps slow enough that you can use some heavy weights, but she herself demonstrates very very light weights. Oh, and she makes fitness comments throughout but after a while the "sexy shoulders" comments and lines about looking good in halter tops gets old. The music in Cory's tapes is soft "porn-type" music (steady beat) but Cathe's tapes have original artist rock music that are really motivating.
As others have said, in Cory's tapes, she expects you to have some equipment and there aren't any really good substitutes for some routines -- like seated rows or pull-ups.
Cory's ab routine is not very long or effective, I believe she does few reps and doesn't put in any oblique work. I just substitute my own routine -- usually Cathe's!!
But I have to say, Cory's tapes offer you variety and they may be suited for beginners and intermediates ... but I'm not really sure why, since you can perform Cathe's PS series with light weights or fewer sets and get great results.
I think it's truly a case of "you get what you pay for". In the end, Cathe's solid routine, right-on-cueing, good form, motivating rock music, (C'mon, we're doing ab work to Doobie Brothers and lunges to Robert Palmer's "Addicted to Love"!) and her challenging workout will take you into the next century. You'll outgrow Cory before she's finished her "sexy calves" commentary.
And I have both tape series -- I've been doing Cathe's PS series at least once a week for over a year now and it still challenges me!
Good luck!
Dawn P.