Depends. Did the new artifact domain with Ayaka and one person had Jean: First the other two died, then me, then Jean.
Then switched to Barbara with three dos (two cryo):
Everyone survived with full health seven times, because enemies froze every second.
Depends on builds and team comps
Barbara provides hydro - admittedly not always well. Xingqiu or Mona would be better sources of hydro (and Xingqiu does provide some healing, but does it worse). (Zoroastaru's example seems like bad team composition issues that Barbara happened to fix).
Jean provides anemo, which means 4pc VV for shred and can swirl elements. Her skill can also cc enemies.
Jean scales her heal off atk, which means she can do damage without compromising her healing ability. Barbara needs to stack HP, and her BiS weapon is a 3* - she's not going to be a significant source of damage.
(Edited by Squirrelloid)
Barbara is more useful, if you need access to Hydro, but otherwise Jean is better.
What do you think?