I really dislike the notion of cleaning in liquids, particularly when soap is added, as it means a step to pour the liquid off and drain it from the inside of the cases to a point, plus extra rinse and drying steps.
Vinegar is about the least painful, and it still requires a simple rinse afterwards.
If soap isn't used, water spots affect the aesthetic finish, and if the water comes from my well, the rinse causes spots.
These are some of the reasons I've avoided fooling with an ultrasonic cleaner.
Vinegar does remove some tarnish, however the longer the cases are soaked, the more frosted their appearance, which is a step in the wrong direction if shine is the goal.