Out of a total of 20 plugins (including YARP, GravityForms, Syntax HLE, WordPress SEO), W3TC ranked #1 by a long-shot, weighing it at nearly 74% on every test I ran. For comparison, I installed WPSC to see how big the difference would be and it came in at only 7%.

Not sure how accurate the details are, as I've not really dove into the plugin or done much more than the basic test, but that's a pretty heavy hit from such popular plugin versus such a light hit from one that's equally popular. I know W3TC has a little bit more integrated with the minification, CDN, etc, though still, does that really make up the 67% difference?