I believe that the collective experience of our organization is that both of the products you mentioned, made and sold by SubTech are very good. As in any remote transaction, go with a vendor that you trust.
If you have a choice, and need a level and depth controller for underwater operation, but want your boat to have a positive angle on the surface such as the Seehunde, (bow up), ask Skip for the devices that have the simple on-off function. I believe they are the same price.
Remember, if you are going to fly, you need a parachute. If you are going to dive, you need a SubSafe.