I have played both of them and my opinion:
-If you plan playing OL you become a completely altered (screwed) gameplay, simply overdosing the replayfactor.
-Monsters (Cat, Burer, Pseudog)
-Driveable Cars (I personaly don't love it, cause in a car you almost invincible.)
-You can join almost every fraction, and the members will help you whit co-op play if you need it. (Its in v1.8, I dont know the avaiability in further or latest versions.)
-And the weapons, yes (Toz34, AK47, etc.)
-Cc. 120MB (v2.0 7z archive)
-If you wanna see how can a 2 year old graphic engine look like a fresh 2009 franchise then your mod is Stalker Complete 2009. You get.:
-Completely HD retextured everithing.
-Shaders overtunned. Wet surfaces, Glowing sky, Depth of Field (I use "r2_aa on" -For me is the fastest way, but in this mod you don't need it.) etc... (The engine realy move on his limits.)
-Athmospheric Sounds. Like a movie. (I like it, especialy the guitaring npc-s, amd the bar radio.)
-Its funny, but on my rig shoc is running faster whit this mod, faster than the vanilla version. Like a fully optimized game.
-Cc. 650MB (v1.4.2 selfextracting exe)
Now I try compiling OL whit Argus' work HD textures and Panorama mod.
Hard work, but I need gameplay(blowout) and eyecandy too.
"Got a job for you Marked One, the choise is yours."
I actually went with the Complete 2009 mod. Its is simply the best mod I have ever played. The game played and worked phenomenal. I might play OL sometime down the road though. Thanks for the input though.