Well, "better" when talking about performance will always depend on things like system specs, how the software is coded and blah blah blah. When I speak of EMET being better than ES as far as protection is concerned, it's because EMET is not limited to a browser or some 3rd party wanting to make more money by limiting protection to one thing or another. Again, EMET covers pretty much the entire system and it does so using protections already built in to the OS. That can make a lot of difference in performance. I'll assume when people talk about it being "heavy", they might be meaning the service that continually runs as of 3.5. In my own case, I noticed very obvious drag on my system with ES that is all but gone with EMET. Your mileage may vary of course.