In all honesty neither really strikes that much of a cord with me anymore. I tend to look more at the bow's physical characteristics and shooting characteristics before I give the speed rating any consideration. However, and again honestly, I probably would not buy a bow with under a 300 fps IBO speed rating simply because I know there are plenty of bows on the market right now that have at least that speed rating and that are also quiet, accurate and fun to shoot.

So I guess you could say the IBO rating.....and on another note, not all companies list AMO ratings for their bows so it is difficult to use it as a comparison figure.