The main difference is if you upload your music (ripped CDs, “acquired” MP3s) with Apple Music, you lose it after you cancel your Apple Music subscription. Even if the files are sitting on your device, you will not be able to access or play them after the subscription is ended.
When you end your iTunes Match sub, you can only access songs you’ve downloaded, they will not be available to download after the sub ends. You can continue to play the songs that exist on your device.
Your iTunes Match library will only be stored online for 30 days after you cancel.
- make a backup of your iTunes “matched” personal music, store it somewhere on disk
- cancel iTunes Match
- continue subscribing with Apple Music, and upload all your personal music with it
You can see the file type in iTunes if you add the new column “iCloud Status”. If you upload an audio track that cannot be matched, it gets the status “Uploaded” in the “Cloud” column.
So to follow the best option above, download and save all items of type Matched and Uploaded.
There is currently (2015-11-18) a bug where content you uploaded with iTunes Match is mistakenly labelled as Apple Music.
So at the time of writing Apple is forcing customers to pay for both services, if they paid for iTunes Match and then later subscribed to Apple Music.