I would say the best feeder are dubia roaches or Turkistan roaches or lobster roaches. Dubias being the easiest and slowest ones. Phoenix/repti/calci worms are 2nd since they are a lot smaller plus unless you have a wine cooler, you really cant keep a lot on hand or they will pupate. Then there are crickets, the embodiment of satan in an insect. They stink, make noise, bite/eat your beardie and anything else, jump all over, don't live long. Only upside to them is they are cheap and readily available.
And yes I've seen Harley change from eating dubias. She got spoiled and turned her nose up at crickets and now she doesn't even care for phoenix worms that much but she loves her dubias. I'm thinking of giving hornworms a try but for some reason those things kind of creep me out and I heard you should crush the heads before feeding them to your beardie or else if he/she grabs it wrong, the worm can turn back and bite your beardie in the eye. Read about that happening on chameleon forums to chameleons. Wasn't a pretty sight seeing the pictures either.