Placing trees as model or terrain

Which performs better, dropping a tree mesh in the scene with a a box collider, or making trees with the terrain tools and adding box colliders after? Is there a difference?

 

First, you should use capsule colliders on trees, just because they match the trunk shape better and are slightly more efficient than boxes.

To answer your question, it is more performant to paint them on the terrain using terrain tools because Unity handles LODing and billboarding them (legacy trees), for SpeedTrees it might not matter as much, but it is much easier to paint them on the terrain using the terrain tools than placing individual trees. You shouldn't add colliders afterward - as long as your tree prefabs have colliders, they will automatically be included when you paint them on the terrain as long as the checkbox "Enable Tree Colliders" is checked on the Terrain Collider inspector under the terrain object.

 

Thanks I really appreciate the info.