Features:
For me, the features of an instance was a major factor. This is the main reason why I switched from a Lemmy instance to a PieFed instance.
Polls, combined communities into feeds, comments from all crossposts in one post, multi images in posts, better integration with Mastodon users, scheduled posts, tags, flair, blurring of spoilers, etc. All good reasons to use PieFed instead of Lemmy.
As far as hopping between instances of the same software:
Content:
I usually prefer instances that give the end user more control over the content they want to see. That means minimizing the number of instances blocked (as much as reasonable) and more federation. Piefed.Zip would likely be the next instance I’ll hop to.
Privacy:
.World instances actively block VPN users. So that’s one reason I would avoid them for future hops.
Politics:
In general, only if the admins block/ban users based mostly on their political beliefs. I try to avoid factoring in whether admins have political beliefs that match my own. There will always be things that people disagree on, and everyone has their own lines that they have drawn on how far they’re willing to support others based on their own beliefs.
What matters to me is that an admin can treat others fairly, even if they disagree on politics.
Domain Name:
Usually not a factor unless it’s something absurd.
PieFed because it has more features and integrates better with Mastodon users.