But shot placement aside,since there are so many variables in it even on "good" shots...

A broadhead kills through several different mechanisms, all driven by hemorrage. More cutting area= faster bleeding = bigger blood trails, and shorter ones, hopefully. More cutting area can also have a negative impact on penetration depth, dependant on the broadheads design (COC vs Mech). But even on a big buck you only need about 14" of penetration for the broadhead to pass through the chest cavity on a broadside shot and leave an exit wound. Angles can be longer, sometimes much longer.

In my mind the most critical item for a blood trail is an exit wound, and for that you must get enough penetration, with a still functional head, to achievea pass-throughconsistently. But after that...