Does loot qualty vary more for co-op than solo?

Will levels drop better loot depending on how many you are playing with?

If so, will the loot quality also vary between 2, 3 and 4 player co-op?

The quality of the loot dropped in a map is dependent on these things:

• The map in question
• The difficulty you chose for the map
• What wave it was when the loot dropped

Loot quality does not vary based on players. However, more loot drops during co-op because you are fighting and killing more mobs. Because of the fact that you are killing more mobs and seeing more loot, it will seem as though there is more variety. In actuality, you're seeing the same variety (percentage chance of drop for each quality), but you're seeing more of it.