For me, Auth0 was the quickest and easiest.
I only wanted read-only social network login.
There was an official library in the language of my choice.
It was free (at my level of use).
The only thing I need to keep secure is the API tokens for Facebook / Twitter / GitHub etc. I don't even bother storing anything other than the user's ID, current name, and service.
If someone hacks my service, they won't be able to do anything nefarious with the user's data.
Building your own is a nightmare. If a login provider changes their API flow, Auth0 are incentivised to fix it - rather than passing the buck to me.