Given a choice between the two, I would pick a non-union shop every time.
In general, unions protect poor performing employees and hinder well performing employees. I had a machine mechanic that was worth 3X what the others were worth (skill and effort wise). I couldn't pay him a nickel more than the others. On the other hand, when someone is habitually caught sleeping comfortably on a bed of corrugated board, the union defends him.
Then there are the ridiculous work rules. A plumber had to be paged to turn on a spigot for a machine washdown.
I could go on for hours.
It is funny to watch these union dolts cheer....as their actions will result in more automation and robotics, along with possible moves to Mexico or another area with lower cost labor. Funny, they are voting to put themselves on the unemployment line. Dolts.