Bard has a finite number of attempts but a Succubus can spam till someone rolls a 1. I'll settle for a good tier 3 though.
Bard has a finite though large number of attempts, yes, unless he's going fullblown diplomancer, but that's generally been a T2 stunt. Charm person does have more trouble with charming a whole room, a more limited list of targets, and I think there's only so long a Succubus can spam charm person before it gets suspicious. Not to mention that charm person can get detected, dispelled, noticed by sense motive, and once it expires people may recognize they weren't quite being their usual selves. But spamming endless Charm Person and Suggestion is still very abusable. I guess part of the question is how much will at-will Charm Person and Suggestion be abused beyond what a normal character could do in a day and how likely is that to bite you in the ass?
How is Magic Jar as an SLA supposed to work anyways? Not that it matters for Shadow Demon since there's a bit of pseudo-errata in Occult Adventures that says to replace all magic jar SLAs with (Greater) Possession SLAs.
The shadow demon jumps in and takes over the target's body until the spell expires or he is evicted. There is no actual magic jar used (the target's soul stays in the body) nor does the shadow demon have a corporeal body he leaves behind.