Source is like an updated half-life engine very close in physics thankfully, I played CS as a HL mod and long b4 steam ,I think they feel the same only 1.6 is faster.To answer ? why play a knock off play the 1st/best is one > Source is too easy I've heard alot and the older computer is valid but it works the opposite way as well.Unless it's changed we couldn't run 1.6 using Vista as OS.....That's why I started playing source 1 year ago.