They're usually interchangeable, ie, if you upload a requested item to Mega, and send the link to the people requesting it (offering points), they will send you points for the link.
However, some want you to also share the asset here, on the site, and a few won't give you points if you don't.
Usually, people offer points, and assume you'll upload the asset to the site as well as share it directly with them.
Personally, I think that any asset you're willing to share with specific individuals, should also be uploaded to the site so anyone can buy it with points, but I know some have other opinions on that.