Vegetation (Prefab) Performance With Terrain Tools vs Without?

I have a level that is about 100m wide and 1000m long. I was originally just using planes for the ground. I was in the process of individually placing various trees and bushes. I wasn't planning on using the Terrain tools for this as there isn't going to be a crazy amount of vegetation (setting takes place in a rural neighborhood. But this got me thinking... With all these prefabs for vegetation is there any performance difference between placing all of these prefabs or painting them with the Terrain system? I've only played with the Terrain system a little bit so I'm not sure how it handles all the instances of things you paint onto the terrain. If the answer also depends on how much vegetation (prefabs) I planned to place in scene without the Terrain tool then I am not sure at this point. If I had to guess somewhere between 100-200. Maybe more.