^ Mojos are awesome bindings. I only put FKS, STH with driver toes, and Mojo(or equivalents) on my skis.
OP: Your dealing with the two top bindings on the market, honestly, you can't go wrong with either. If it was me I'd get the cheaper one.
-Awesome elasticity and smooth consistent release through the turnable heel
-Burly all metal construction, these things last ages
-Light for an all metal binder
-Small footprint allows ski to flex more natually
-Puts you super close to your ski.
-Have to bend brakes on wider skis
-Need to make sure theres absolutely no snow on your boot/binding when putting them on in pow
-Super adjustable toe peice to make it fit super snugly to your boot toe. Good for worn boots
-Also got burly construction
-Spheric release toe which is an awesome toe piece
-Lighter than the FKS
-Wider hole pattern less prone to ripping out but i've never had a problem with FKS personally.
-Some parts are plastic
-Can need frequent adjustment
STH's are going to be easier to pick up cheap in BST here or TGR due to the larger supply available, but if you have rossi connections it doesn't sound like that will be a problem. That being said, your not going to be getting any big discounts on FKS even if you know people. STH 16's can be had brand for $150 reasonably easily if you spend some time looking for them.