I've been feeding my four b. medica crickets that I've raised myself, and haven't had any problems. I do make sure they are small enough to easily handle, and take out any that aren't eaten by the end of the day. So far so good.
My mendicas handle crickets just fine. I've read and heard that other empusas ie. Idolomantis diabolica do not fair so well when fed crickets. I give my mendicas hydei, mealworms, blue bottle and house flies, and crickets.