Different, yes. More balanced... uh... not to a significant degree if that's true. But in both games the better player wins. The winner of equal players is often determined by their cash. As for buggy, as you said the Half-Life engine is a lot more mature. However, CS:S is constantly improving and at the current state I really don't notice any more bugs than in 1.6. (unless you count the corresponding *TV features, which Source is severely lacking) This changes with every patch, though, but that's the nature of constant development and I'm willing to suffer a little for the privilege of updates.
So, as of now, I play Source, but I watch competitive 1.6 matches. I find Source to be more fun, but 1.6 is often more interesting competitively.