Source just looks so much more realistic... while 1.6 is like a cartoon. I personally liked both but source just appeals to me more because of it's overall gameplay and look. The only problem is... source is starting to give me, as well as many others, skipping problems. My gameplay skips... or more like... stutters, locks up, "lags" if you want to call it... even though my ping is perfectly normal. It usually happens when I first load and when I fire my weapon. People claimed it to be fixed with the new patch... but mine still does it. I'm still looking into how to fix it...
