I'm still not completely sold on the 'necessity' of the live-action 101 Dalmations, but in deference to millions of other Disney fans, I'll admit the first romp with Glenn Close was nicely done. Like anyone old enough to remember seeing the animated version as a kid, I had a few melancholy moments watching the remake, noticing bits that had been updated or altered to make the story more contempo.
Making Cruella (or more precisely, Glenn Close) the star of the remake suited Disney and moviegoers just fine, but I think her casting tips the balance of the story toward spectacle. The improved animation with CGI tips it even further, although it's hard to fault the production for using the best modern tech. I guess it's all part and parcel of trying to make a twentysomething film palatable to a modern audience. In my opinion, the original film has less visual dazzle but a lot more character as a whole.
As for buying this twofer instead of just one of the films...it's completely a matter of personal tastes. If Glenn Close was one of your biggest reasons for enjoying 101 Dalmations, the sequel is probably a must-view. The movie is almost entirely hers, as Cruella is given the lion's share of characterization and screen time. The supporting cast is affably anonymous, with the exception of Gerard Depardieu, who must have sold his soul to Disney to get stuck in such an apalling role. (Gratuitous humiliation: Gerard's Van Pelt winds up face-first in a toilet.) If you found yourself slightly disappointed by aspects of the 101 remake (like the fact that the dogs didn't talk any more), the sequel isn't likely to improve your opinion (even though you'll get a talking cockatiel with the voice of Monty Python's Terry Gilliam).
This DVD set has the usual Disney extras, at least for modern releases, so you can expect subtitles, some "making of" docu-footage and (drumroll please)... a garsh-honest DELETED SCENE from 102. (In it, Cruella is released from prison...but don't blink 'cause it's a short segment.) Put these bonuses together with the features and you have, IMO, a little four star bundle of entertainment to enjoy. (My personal rating for this package is about 3 stars, but I've adjusted my final rating to reflect the belief that most young kids will love these films in all their live-action spectacle.)