Where you're using the camper should also factor into your decision. You're not going to haul a stack of pallets or concrete blocks and beams around with you if you are full-timing and staying in one place hundreds of miles from home for weeks at a time. It's a whole other thing if you've just got it parked in the backyard as a guest house, or you're staying in it while your house is renovated.
IMHO the best bang for the buck is the plywood X-stands.
The problem with jack stands is that they're still only POINTS of support. No matter what you put on them or under them, they only support from the cradle, which is going to be unsteady to a degree.
A plywood X-brace has 8 feet of contact on the camper, and 8 feet of contact on the ground (i.e. four legs, each two feet long).
