Mike,
From speaking to a few in the know and not much from personal experience.
Your run sounds more like a thresher, with the multi directional movements or a porbeagle that has no idea you're there. Dave's sounds much more porbeagle than anything else with a long sustained run albeit a bit sedate. Seen this, but faster, a few times. Twice, when we saw the fish before it headed for Rio without stopping.