B) is basically what we have already. Contractually only required to work 40 hour weeks, no [official] pressure from management to work more, but anyone who does will most likely have higher output / receive better performance bonuses and recognition, etc.

The only thing a union brings to the table in this situation is now I'm either explicitly forbidden from working more on a project even if I want to, or I have to hide what I'm doing and go all cloak-and-dagger about it, probably breaking some kind of labor laws in the process. All for 1% of my salary. Doesn't seem like a good trade for me?

It seems like in the scenario B) has the added teeth of deterring leadership from forcing unpaid overtime, as some management do, though it is possible even with the union-enacted mandate they will still try to sneak it in, as you suggested.

> I'm either explicitly forbidden from working more on a project even if I want to

This sort of nitpicking is always cited as a reason for why unions are bad but would a union really get up in your case over something like that? And furthermore, would a tech union birthed natively in this industry, created and populated by tech workers who have also worked spent evenings or weekends voluntarily to work on projects they themselves were passionate enough to finish, really penalize its all members for doing the same? Wouldn't they, you know, have an insider's insight of the needs and interests of working in tech?

I think not. The idea is to guard against when management oversteps its boundaries, not to police other workers. And if the union inevitably does fall short and do the latter, then by being part of a union, you would have the power to make changes within it.