When would a Heracross benefit more from a Choice Scarf more than a Choice Band, and vice versa?
Burn Orb will kill you really fast if you're eating residual damage (Spikes, Stealth Rock, Sandstorm).
Honestly, I think the answer is, whatever your team needs. If you want more speed, then Scarf. If you want more power, then Band. If you can't decide between the two, then mix it up - sometime Scarf, sometimes Band. You'll either find you like one better, or you'll be able to keep your opponents guessing.
Heracross should be a Scarfer, no questions asked. Hera's speed ain't exactly his highest stat at only 269/295 Max. Plus, a lot of Pokémon set their speed to 270 to beat Adamant Heracross. Its generally safer to run Choice Scarf because a lot of common OU Pokemon(Salamence, Azelf, Weavile, Aerodactyl, and Porygon-Z)outspeed it w/o Choice Scarf. If you really wanted a CB feel, you could simply switch into a Will-O-Wisp or something. But thats just me.