I've used a grubber and it pulls the brush/tree out of the ground roots and all. You should remember to attach it on small trees about one foot up with a long chain. And the tractor attachment is low down, like on the drawbar.
When you pull, the tree will fall towards you and the tractor, hence the long chain. You attach to the tractor low down because of leverage. And the one foot up the trunk is the best way to pull the plant out.
One inconvenience is that the grubber's jaws bite into the trunk and are hard to remove. I use a rubber mallet for that.