Well, I think bebi and Ei are fundamentally different. Bebi is mainly yeast and rice bran, whereas Ei is purely bacteria. They accomplish similar things, which is becoming a food for baby shrimp, but I've never seen shrimp quite go nuts for Bebi as they do for Ei, and I've used and sold both in the past. Ei is pretty unique, shrimp seem to smell it right away and attack. The babies grow up pretty quickly on it too.
It's also something that my cardinals will eat, and they wont touch anything else (aka, spinach, other prepared foods, fish flakes, etc.)