I have both and have used both, and I feel both have their place. The predator is smaller and more packable, fit inside my pack nicely with room to spare for additional layers, etc. This is definitely going to be the more mobile of the 2, and you can cam this over solidly and tightly. However, in the tree for long several hour sits it wasn't a natural sit, feet can't get shoulder width apart. The Ambush, by design, is bigger and packing is a bit more of an issue. You can use the provided backpack straps, or strap to the outside of your pack. Additionally, you can really get it to cam into the tree, so much so that camming over can be an issue. Using their process you can get the Ambush very solid. In the tree is where the Ambush shines. For long all day sits my stance is more natural such that I can have my feet shoulder width apart or together if I so choose. Also, I can move around on both (specifically off side shots where you stand and turn) but because the Predator is smaller, your movements have to be more deliberate, where with the Ambush you have a little more room to turn. I am comfortable doing so in both (shot 2 deer from the weak side from the Predator) but you have to be more cognizant of your feet when making that move on the Predator.
Both of these have their place and I will continue to use both. If I am going to be scouting around & picking a spot, ala "run & gun", I'll opt to go with the Predator as it is a couple lbs lighter and more compact. If I have a spot that is already picked & prepped, &/or will be sitting all day, I'll use the Ambush.