The pros I see for Lemmy are a better platform for discussion, and the posts are ranked by votes. However, the cons are that the content isn’t tagged, and many times it doesn’t even provide the source.

Lemmy also offers a greater variety of content, including not only images but also stories and audio.

If there was a booru that ranked content by votes, I would probably have gone there, but as it is, I think Lemmy is better.