it's the same principal of using one lemmy/piefed mobile client over another. my comments are still going to the fediverse, but if you're using one software, you aren't supporting the growth of another. even if other instances can see the things I post, that's not their growth, since at any time I can cut them off if I do not like the behavior of their users.

as for features, piefed has a few significant things that lemmy does not have. for example, problematic users have a big red or yellow warning sign next to their name everywhere they go, showing that that person has low or very low reputation. at a certain threshold that I set, I can also automatically hide downvoted posts and comments. there's also built-in user notes, so I can tag users and have that tag display next to their name as well.

and finally, piefed has actual user/instance blocking. for example, we found out the hard way that by having .ML as an instance blocked in my personal settings, no .ML users were able to comment on my posts or reply to my comments at all, even though my instance is federated with them.

there's also a lot more settings when it comes to communities. while it was still on lemmy, we used to have a lot of .world users downvoting every post in !libjerk@anarchist.nexus, simply because they found the content offensive and did not interact in any other way. downvotes affect discoverability in /all, so those liberals were in effect trying to censor us because they don't like being criticized. we've even had to deal with people using alts as zombies for downvoting. now that we've moved the comm to piefed, we can restrict the people who are allowed to downvote as much as we want, so that sort of abuse is impossible now.

I made the switch some weeks ago and can only speak of my experience using Voyager: The switch was flawless.