They are only guaranteed until some elected official decides to give you a haircut on your deferred paychecks (Which is what a pension is), right as you're about to retire. (Or shortly after you do.)
I'd hedge, and prefer splitting my money between both.
Unions? Government employees? They aren't even on the top ten of 'most powerful organizations in the country.' Not for the past four decades - Ronald Reagan fixed that glitch.
What's going to happen is that paid shills will start publishing op-eds citing a handfull of executives and upper managers who gamed the pension payments system with overtime, resulting in massive payouts for themselves, drum up public outrage about lazy government workers, and pass an across-the-board haircut. It will, as always, be turned into a red vs blue issue - and half the time, red's in charge.
But you exchange a lower salary for that government job, which makes saving for your 401k & co less effective. There is also the entire calculation of the expected value of money now vs 30 years from now.
I'd hedge, and prefer splitting my money between both.