Maybe for your average everyday "I play once a month" guy, CS:S may be better b/c the graphics and it's noob friendly play.
CS 1.6 is just that, it's classic. One of the best FPS to ever come out. It's been around since '04 and it's still more popular than CS:S. Look at some of the best CS 1.6 players that jumped to CS:S when it first came out b/c that's what sponsors wanted, they all came back to 1.6. You can say what you want, but I play a lot of CS. I have free time and my son's mother isn't much of a mother so I'm always home. I've played CS competitively for years from CAL, CEVO, ECO, etc. For competitive play CS 1.6 is the way to go, it's not as noob friendly as CS:S.