The main difference is that properly paid civil servants can't be bribed like if they were working in a third-world country,
WHAAAAAAT! You can't be serious! They are bribed all the time! Not just that, quite a few extort money. Our Massachusetts Speaker of the House just went to jail for taking money from a Canadian company for a state contract!
Perhaps on the congressional level - one of the inside secrets of congressional life is that they spend more than half of each day looking for funding - but on the ops level it's a known fact, learned by sociologists who did a study, that if you pay civil servants enough to live properly, then their inclination is not to corrupt, because they tend to like their job if paid enough for it.
If you've ever traveled through Mexico, you'll know that the way to get through a day is to bribe the local officials, and it just gets more extreme the further south you go. Currently it's not possible to do that in Canada nor the US because so-far the civil servants are being paid enough that you'd have to be involved in something astronomical and the level of bribe would have to be over the moon and past Pluto for there to be a chance, and even then you'd probably have to threaten their wife and kids, and even then you'd just be making things more iffy.
An interesting example comes from the former Soviet state of Georgia.
Like all ex-Soviet states, their cops were corrupt, because they weren't paid enough, which means they also didn't give a hoot about the moral purpose of their jobs, because of the hypocrisy.
Georgia did something interesting. They sacked 2/3's of the force, keeping only the ones with a natural sense for the job, and *trippled* the keepers salaries. From the state's point of view it was costing the same, but now they had cops who were actually keen to do their job, and were *way* less bribe-able.
And yes... with that 1/3 sized police force, enforcement became more efficient and the streets became safer.
So... hmm... do civil servants need unions?
I dunno. People don't unionize when management and ownership have enough sense and wits to make it so workers don't feel a need to unionized, and you can tell when you've got doofus in management when the only way they can think of to not be employing unions is with threats of psycho-tyranny.