One comes from a manufacturer who actually cares about getting their devices timely updated, and officially supported by 3rd-party ROMs such as LineageOS. Should your phone break, they have a pretty much worldwide service, all you need is to ship back your device according to the instructions. The other is an "shady" operation that installs all sorts of dubious apps and build-in advertisement in their iPhone-esque stock ROM. They lock your bootloader for an arbitrary amount of time that is usually 1 month, and in order to get it unlocked you have to provide your phone number and access to your personal data for the duration of the wait period. Should your phone break, they'll just make up excuses in their laughable "global customer support". If you are lucky, the store will repair your phone, not that crappy manufacturer.
If you don't know which is which, then you are a really poor customer that does not do his homework.