I think either one are fine. I think bottle flies are a little bigger.
You can gut load them. I got this from the Kammers:
Gut loading:
Since the flies emerge with empty stomachs, you will want to "gut-load" the flies to make them nutritious for your chameleons. You can mix a soft-boiled egg (mashed to a smooth consistency) with a few teaspoons of plain yogurt, baby rice cereal and some honey. Once cooled, take the culture out of the fridge and knock the flies down by tapping the container to one side. Carefully open the lid and smear a generous teaspoon full of fly food to the side of the container. When the flies warm back up to room temperature (within minutes), they will immediately begin feeding on the yogurt mixture. Two to three hours later, they should be ready to feed out. From this point forward, the flies can stay out. You can gut load any remaining flies the next day, by following the same procedure listed above.
My recommendation is to make sure the mixture is dry and sticky. I drowned a whole culture of pupae with a runny gutload once.