The downside is ease of use. Not everyone wants to set up a mastodon feed or a Lemmy feed. Lots of users only want one specific type of post.

For instance, I hate the Twitter-style microblog. I choose to use Lemmy because I specifically want to exclude Mastodon posts from my feed.

There’s also the issue with app development. Apps for Lemmy have undergone a lot of development in the past few weeks. Apps for kbin are basically non-existent. This is an issue that could be solved with time and the right developer(s) but as it currently stands a mobile user will be better off using kbin in their browser. So if someone is looking for a more seamless transition from Reddit, the natural move is to Lemmy.

Lemmy doesn’t currently work with Mastodon, and I don’t think there are any plans to change that. So the two platforms, while both federated, aren’t truly compatible.

Kbin (kbin.social) is a sort of in-between service. You can follow both Lemmy communities and mastodon accounts. It has two different halves, with a feed for Lemmy and a Microblog feed for Mastodon posts.