I use both. Tangled is missing some important features (private repos, protected branches). The ui feels more comfy to me, though. And Codeberg is quite slow for me.

Idk if I can give you toooo much about migration, since I haven't used any CICD kind of stuff; just having repos to push to is super simple if you use their hosted knots. Also not too complicated to host a knot yourself; I'm hosting my own knot, and I like that I own at least one of the servers that I'm pushing code to.

What makes Tangled different from other forges like Forgejo/Codeberg is that its built around the ATProto federation protocol