I've used the MKII 20mm, IR Patrol m300w, and a buddies Reap-IR. i just got my own Reap at the end of January. I've also used ATN Thor, Armasight Predator, and Pulsar xd50. It's real hard to beat IR Defense products in my opinion.
Was going to upgrade my MKII to the 35mm version but have decided not to. If you do a lot of spot n stalk in wooded areas, the wider FOV of the 20mm is much easier to scan and maneuver. For open fields and longer shots, the Reap is where it's at. You get a whole lot more detail with the 2.5x native magnification and saving multiple zeros makes swapping between primary rifle and rimfire critter poppers real easy.