Using different Apple IDs keeps everything separate, photos, media, apps, purchases, subscriptions , voicemail, all of it.
Using different Apple IDs mixed together on the same device or same Mac also means tracking which Apple ID purchased what, as updates require use of the same Apple ID.
There is no means to migrate purchases and subscriptions and apps among Apple IDs. It is feasible to move photos and mist (all?) personal data among Apple IDs.
Using the same Apple ID means that conversations in messages, voicemail, media, apps, photos, and the rest are available everywhere when using that same Apple ID.
For keeping business and personal stuff completely separate, use different Apple IDs.
For most other environments, use the same Apple ID everywhere.