I am finding that the perceived exertion method is more accurate per individual. I'm not saying that I don't agree with taking a heart rate check or that I will never use it anymore, but rather that I find the perceived exertion method to make each individual become more in tuned to their own body and needs for modification. While heart rate checks are good general indicators, they are not 100% accurate. But when you are working so hard that you are gasping for your last breath and/or unable to talk in 2 to 5 word sentences, there is just no mistaking that.
I have used the perceived exertion method for years and I really prefer it to the heart rate. When you have exercised for years (16 years) I feel it is a much better way of knowing how hard Iam working because I have gotten to know over the years how to listen to my body and how I feel as I work out.