My NRC conversion uses a leveling system made by Equalizer Systems in Elkhart, Indiana. www.equalizersystems.com
They appear to be similar to Big Foots, in that they are quite heavy duty. I think the main difference is that they use one hydraulic pump for all four levelers rather than a seperate pump for each leveler. They have an auto level function as well as individual control over each jack. Also, an auto retract for all four jacks.
I initially had some problems with them but their service is very good. After replacing a leveling sensor all is well. The jack will easily lift the entire motorhome off the ground. My MH weighs in excess of 35,000 pounds.
At one campground that was particularly sandy and uneven, after putting some 4" x 12" timbers under the rear jacks they leveled it right on the money.