I've used
FlatOut Off-Road because the rubber chunks in it will plug a hole in a non-tubed tire pretty quickly. I've also used on-road, which also works great.
What a friggin' mess when pulling a tire though, which has to be done if you're going to plug the tire because the FlatOut or Slime or whatever will interfere with the vulcanization of the plug goop. Cleanup with a garden hose or pressure washer is definitely doable, but man did I get wet (in the cold) cleaning that mess up (rims and tires).
With that experience I have lawn (the front have tubes added), industrial, and agriculture tires for the BX and run the appropriate tire for the job. If I were running over spines and puncturing tires (like some members here) then I'd probably use FlatOut Offroad to extend tire life.
The "self-balancing" of on-road Slime or FlatOut does work to a point, but for me I had to go 85 to get it to spread out and balance on multiple vehicles when dosed properly according to their instructions per each tire/wheel size, at which point it was clear it spread out and worked well. As a note, if the imbalance is beyond a certain point the wheel might not balance at all speeds, so "35 MPH and below" and "65 MPH and above" might be great but 45-55 not so good.
Once the tire wears to the point the additive can no longer balance it the additive has to be removed in order to spin the wheel on a tire balancer. For something like a Polaris Slingshot where there's no spare tire additive makes sense, but if you can carry a spare it's
probably best to not use Slime or FlatOut.