I think the sus tends to give you more size due mainly to water weight. They are both test but the sus is a blend of test and A. Roberts just wrote a good piece on how the longer esters like in sustanon give you more estrogenic sides like the weight gain and even strength gains when compared to the shorter esters like in prop. So if you're going more for the hard look go with prop, going for size go with sus. With prop you'll need to inject ED with sus EOD or even E3rdD. GL