The Loot Pouch, being the most common, usually doesn't contain much of value; mostly Crude Items, collection valuables, and gold. However, if your luck is good, you may find a nice surprise inside (such as a bright or dark black clothing item or even a Famed item, though highly unlikely).
The Loot Chest, being the second most common, usually has ordinary items: gold, collection valuables, Crude or Common items, and things of the sort. However, you may occasionally find a bright or dark clothing item or even a Famed in these simple-looking wooden chests (on the rarest of occasions, Legendary weapons have been found).
Finally the Loot Skull Chest: what every looter hopes for. Being the rarest and by far the most valued, they can contain just about anything from a Famed or even Legendary weapon to a rare clothing item to sums of gold over 1,000. These are, by far, any looter's best bet at finding a Legendary weapon.