They might do the same job. They just do it in a different way. They look differently, they work differently, their key concepts are a bit different, their workspaces and workflows are differently organized. Plus, Logseq is fully open source while Obsidian is not.
It’s not about features. Almost every notetaking app has pretty similar feature set today. I’m talking about the approach in general.
I suggest you to install them both and take a look. Or even better - use them both side by side for a while ;)