If you ask me, the Source version didn't include any QoL improvements or anything that might make the game more modern feeling.

The "upgrades" are mostly new textures and effects that bugged out half the time. Plus all the gameplay bugs that it introduced.

Even before the update most people were recommending the OG above the Source version, so it makes sense that they would update that one.

The one just named "Half Life" is the definitive version now, the one that got the big update yesterday.

Source is the same messy version as it was before and they haven't touched it. Though it will still be in our libraries for legacy versions.

Valve themselves recommend you ignore Source exists now.