The biggest different is that when properly used, hammocks can eliminate much of the impact generally associated with tent camping. When tent camping, you are impacting a larger area just by the sheer nature of a tent’s size and the additional impact of sleeping pads, sleeping bags and the campers inside.
As long as ‘tree saver straps’ (2-4” wide straps that go around the tree to minimize any girdling effects) are used, there is very little impact associated with hammock camping. Besides getting in and out of the hammock, the ground beneath is almost untouched. Additionally, a hammock allows for greater flexibility when choosing a campsite. When looking for a tent site, level ground is generally preferred. However, with a hammock, one can essentially camp wherever there are trees. This could be on a steep slope, over boulders, snow or other surface the might not be suitable for tent camping.