My impression of mixi2 is that they've done a lot of research on Misskey.

The elements that are considered to be advantageous to most people compared to Misskey are:

- App available (official only, no room for hesitation)

- Closed

- Simple and excellent UI

- Lightweight app

- Strict rules on prohibited activities aimed at the general public

- Managed by a long-established SNS company with strong capital and profitability