I have Rimguard in my rear tires and I'm pretty happy with it. I wanted it for the weight ballast, the lower center of gravity and also for the very low freeze point. I think the coldest its been here since I got my tractor was -45F (that was ambient temp, not that fake "wind chill" stuff). That was when my tractor still sat outside year 'round. I do have a box blade I use for ballast in conjunction with the filled tires. I would like more 3pt weight than the box blade, but I seldom lift max weights anymore. I haven't had to move a round bale since we moved in summer of '20. About the heaviest things I've moved since have been my gunsafe (1K pounds) and IBC totes full of ash firewood.
I can see where a dedicated ballast box would be handy for very tight clearance work, but I'd have a hard time buying one just for weight. I "need" (not really) other attachments more, like a tiller, snow blower, etc. Hard to just buy an empty box and toss sand or concrete into it.
My 6' brush hog makes a great weight, but like others have said before, it sure is a lot of length to have to swing around on the back of the tractor.