Is there really any reason not to play Half-Life: Source? I'm sure if you have nostalgia for the original version that might overtake you, but he obviously does not. I do agree Half-Life is a good choice, it blew me away at the time and changed what I wanted from a shooter. I still love Doom and Quake, but having that extra narrative and variety element really added something to the genre.
Half-Life: Source is completely broken. More so since they lazily ported it to the newer version of the Source engine in 2013, but it was always like this to some extent. It may look a bit shinier on the surface, but pretty much every script is broken in some way, and most of the differences are just from their not caring enough to correct things instead of any intentional change. From what I remember:
- DXT compressed textures (everything looks blockier than it used to)
- Inaccurate chrome effects, which were then broken in the update (schru seems to be confusing this with the added specular effects on textures, which were also actually kind of lazily done as they just used the same generic environment map for everything)
- Decals are black, rather than using their original colours
- The original lighting colours needed to be gamma corrected in order to appear correctly in the Source engine, but instead they just modified the uncorrected values slightly or not at all. Brightness and fall-off is handled differently, too, which results in similar errors
- No randomly tiled textures
- The MP5 does the same amount of damage as the pistol, and has exaggerated recoil
- Broken armour on enemies, and now even broken hitboxes (the helicopter's hitbox is a lot smaller than it appears, and tentacles are completely non-solid and harmless)
- Random assets from HL2 occassionally thrown in, which just look out-of-place and stupid
And so on. NPC behaviours and scripting and whatever is also all broken in various ways, but it's so ubiquitous that it's hard to point out anything in particular. The whole thing is entirely on accident. Also, no mods.
The thing about the lower resolution textures in the original also affected OpenGL, not just Direct3D. It can be disabled with a command, though (gl_round_down 0).