I think it really depends on the kind of tree you are planting and you specific environment. I can tell you what works in my area, but that may or may not be the same for you. I have lots of native persimmons in my area. I mostly graft established trees above easy deer reach, but I have planted persimmon seedlings when I want a tree in a certain place. I don't need to protect persimmons at all from deer. I have had rabbits kill small persimmon seedlings but that is it. The next example is chestnuts. In my area, they are not really favored or sought out for browse by deer. However, what I found was that they do need tree tubes to protect them from deer. Here is why. Deer are browsers. They don't graze for long periods. Instead, they mill around taking a bite here and there. Most of my chestnuts are planted in open areas with a clover base. Deer come to feed on the clover but as they walk by a tree they will take a bite. Often times if the seedling is small enough, that bite occurs on the central leader. So, I can end up with chestnut bushes rather than chestnut trees. I find tubes work pretty well for this application. I like to use PVC stakes with my tubes because they bend in the wind giving the trunk some flex. Finally, we come to the much more highly preferred browse trees like apple. Here, I use remesh (cement wire) cages. I like these because they are heavy duty enough to stand on their own without support and don't bend when pressured by a deer. A single t-post will hold one in place. I then use rope to create two Xs through the upper middle of the cage. These form a square in the middle of the cage that the central leader goes through. Sometime apple seedlings can grow fast and lean to the side of the cage where deer can get at them. This square in the middle limits any lean (wind or not) but still allows the tree to move normally in the wind. This is needed to stress the trunk so it does not become brittle. A 5' diameter cage works for me. The holes in remesh are large enough that a small doe or fawn can reach into the cage to browse, but I don't care about lower lateral branches. I'll prune them anyway if the deer don't.
Thanks,
Jack