I have both EA and DD. I use them just for fun. I actually DID use EA to aid in the design and component selection of my engine (not yet fired). But whenever anyone asks about the HP, I am always careful to qualify "my dyno simulator says . . . ". EA is a little optimistic, especially with hydraulic roller cams. I recall reading a magazine test comparing different cams, to see how a solid flat, hydraulic flat, solid roller and hydraulic roller (with similar timing) would compare. I charted those (and many other test results) from magazines to try to calibrate my simulatar. Not perfect, but better than being totally deluded. EA is optimistic pretty much across-the-board, but particularly with hydraulic roller cams. I don't recall exactly, but I think it was somewhere around 5%.