Mastodon is easier to deal with as regardless of which instance you sign up for you are just following other users or picking up on global trends. There is also ONE OFFICIAL mobile app out there to make getting started easy. You just find it in your app store.

Lemmy is a bit of a mess:

• Bad name (yes I kind of resisted due to this)
• Communities you only see your instances and ONLY other instances that users on your instance have subscribed to. This limits your discovery of new communities if you are self hosted or on a small instance.
• Duplicate communities all over for common words just on different Instances. Subscribe to your local one, most popular one, or all of them?
• Need to pick your instance around moderation, but your instance may defederate what ever it wants.
• Nothing related comes up if you search “lemmy” in the iOS app store at this time.

Not trying to nit pick but comparing the two, Mastodon has a few things going for it that make adoption much easier