Signing into the iTunes Store gives you streaming/download access to any unhidden purchases that are available from store and not already downloaded to your library. iTunes Match allows your own locally stored music to be added to this cloud library along with your playlists. Files in your library may either be matched with content in store (occasionally incorrectly, e.g. clean vs. explicit or a slightly different version) or uploaded allowing the same file to be streamed/redownloaded to a different library or device. None of the content in your original library should be altered or replaced, unless you specifically choose to remove some of those downloads to save space and later choose to download the cloud items, and then only if they have been mismatched. For this reason it is always best to take a complete offline backup of your library before starting an iTunes Match or Apple Music subscription. Locally stored content remains yours when the subscription is cancelled, but you lose access to anything stored only in the cloud, apart from your purchase history. Apple Music is similar to iTunes Match, but also allows you to select other content from the Apple Music catalogue and add it to your library and/or playlists, where it can sync between multiple libraries and devices. Any Apple Music content added to your library contains DRM and will cease to work when you cancelled subscription expires. In the early days of Apple Music an iTunes Match subscription was also needed to ensure that your own matched tracks didn't get DRM applied if they were downloaded to a second machine. This is no longer necessary.
If you only need the iTunes Match features then iTunes Match is the cheaper product. Using those subset features as part of an Apple Music subscription will simply cost more, it won't work any better.
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