if it's a choice between ara and sust, i would recommend ara. I have heard better things about it. I just started a cycle using 500mg/week of ara one week ago, and I'm pretty excited. In january i tried a cycle using 500mg/week of sust and I got the infamous sust-flu. except i got it so bad that no matter what i did i couldn't eat, had no energy to work out, and i had no choice but to end my cycle early.