There is a pretty big difference. Most casual skiers like adjustable (or demo bindings) because they can adjust to any boot size and they can loan to their friends. Some park skiers like them because they can mess around with mount points- if you want to experiment with true center, you can move the toe and heel forward on the tracks, and if you want to try a rearward mount you can slide them back a bit.
Negatives include a super high stack height (how high you are up off the ski), messing with the flex (which was already mentioned), and they break easier. More fiddly parts = more that can break.
 It also depends which demo bindings they are. Demo attacks and Demo wardens are the best demos in my experience. With all that being said, some people short on cash rip on demos. A buddy of mine has old PB&Js with demo griffons that have seen gnarlier stuff than my pivots ever will.
Pivots will cost you $250+ if you find a deal and $60+ for the mount, (or $150 + mount for attacks) and you will probably only get $100ish back depending on what type of demo binding you have.
Either way i think its a viable option. You could keep the demos, experiment with mount points, and save some cash for new boots or pivots next season, or you could get your setup dialed. Ive done both and been happy both times.
**This post was edited on Nov 6th 2023 at 12:18:28pm