Draenei is a free HoT that can’t be interrupted beyond being dispelled. It can also be used on others. Basically a mini cooldown just for being a draenei.
Zandalari is only on themselves, channeled so their locked down, and they need to escape danger so damage doesn’t interrupt it.
Personally I think Draenei is WAY better, but zandalari can be good on rogues, mages, and other classes with instant escape abilities or invuln.