Hmm. I try to keep physics props in my maps, and I haven't noticed a difference. Being as though a ragdoll prop is approximately 100 times as expensive as a physics prop, I don't see how it could make an impact. Heck, even with a room full of ragdolls (I was testing if my scaffolding would cause lag, so I turned on insta-respawn, insta-death and bots) I barely noticed a difference in comparison to material drawing and prop rendering (yes, it is pretty optimised, thanks for asking). Anyway, I find that physics props are a combination of left-overs from hl2, realism/continuity and a little bit of gameplay. If you're wondering about that last part, I personally use the cones in hydro and barrels in dustbowl as a communication device to say "we've set-up base, come on in".