Reading through some back threads from 2008 (warning: you can get stuck all day doing that) someone brought up a good point for top entrances. When foragers enter through bottom entrances, they have to pass through the brood nest to get to honey supers. Therefore more honey ends up getting placed in the brood nest. If you stick to top entrances, they come in with the supplies and travel downwards, hitting lots of available frames on the way down. Hadn't thought of that before, thought I'd pass it along.