So through a variety of work-related drama that really doesn't matter, my direct manager's position has opened up. I've essentially been doing the job but without the title for a fair bit of time so I decided I might as well try to get the position officially. I later found out that the position I applied for isn't actually a union position and it's kinda made me start rethinking things, as far as I'm aware it shouldn't actually affect the benefits or hours, just a non-union unit manager position.
Depends on how risky the management position is.
I assume the Union doesn't allow its members/represented workers to be fired without cause, so you'll lose that. But if management and the Union aren't constantly at each other's throat and the workers are content with their wages/benefits/work environment you'll probably be fine.
That'll change when upper management starts to be shady and you'll be expected to toe the line but that's a bridge to burn some other day.