If you aren't real familiar with the discharge characteristics of Lipos, Use 9V soft cut. If you can tell when your cells are starting to drop off, you can use 7.2V, but you risk screwing the pooch if you can't tell when they are going flat. You can easily ruin your pack if you press it.
Best advice: If you aren't sure, use 9V and soft cut.
Best advice: If you aren't sure, use 9V and soft cut.