Despoil, most of the time. Otherwise, usually whichever was triggered first (meaning if the spell was played before the champion was deployed, or vice versa).
It's deploy order or cast order. So if you deploy a champ with soul collection before your opponent uses despoil, you should grab the globes. However last I checked the consistency of soul collection is poor and occasionally it doesn't even grab globes until you move, so I wouldn't rely on it.