Also consider what kind of work you typically use the tractor for. As is, with no ballast, they can be useless in some situations, snow or loader work if so equipped given the traction and balance offset by the loader. In some situations you may not need it, but as a general rule, these and most tractors will have traction issues without some kind of ballast. The difference is great, and I have compared this on the same tractor, no ballast, then rear weight on the 3 pt hitch, then with CACL ballast in each rear tire with the rear weight on, the latter gave the best performance.
CACL like was said, will work fine, and give the maximum weight per gallon of liquid. There are pros/cons of each, consider puncture risk in areas you will work. I regularly worked with my CACL loaded 4 ply firestone field/road tires in the woods and or brush, as well as regular tasks, but if you have vegetation with large thorns that is capable of puncture, (honey locust or similar) you may want to consider weights. They are around, the prices vary and you may have to travel or pay for shipping to obtain them.
I would agree with what was said about CACL ballast in regards to timely repairs or any maintenance. It seems you will need to change the valve cores every so many years, my 850 is due as when I pull the metal cap off the stem I have a drop of liquid, but that cap does not leak, yet. Spin them to 12 o'clock,(valve stems on tires), have a water hose ready to rinse off any CACL, change the core and wash it down with water thoroughly. I have another tractor that the previous owner allowed the valve stems to leak for a long time, so far the valve holes seem to be fine, but the surface rust on these rims in some places is substantial. I have not been able to deal with it just yet, but will before the summer, we will see what the results are. Sad, because there is plenty of time to change out a leaky valve core before the previous happens. We have a '00 NH fwa, 80 hp in size I believe, at the stable, it had new tires all the way around. It was a low hour tractor that came from a school with turf tires, it has rim guard. I may do the same if I get new rims, as it seems comparable in weight but if the old ones are repairable I'll go with CACL again. I loaded my 850 rear tires with CACL in '08 and its just now time to change the valve cores, there have been no other issues, and I did all the tire work from blasting the rim clean, painting, tube, tire and fluid. I have experienced a valve stem failure too, no different than a puncture, the fluid will rush out and you just hope that what is drained out does not kill vegetation or trees etc, that you don't want dead. Mine blew out while I was standing there in the yard, so I grabbed some pans and a garbage can to retrieve what I could. Faulty tube that leaked, and this was done by a tire service, it did ruin the valve hole in a new rim, but I was able to repair the rim. Seems you had best find the best quality tube available if possible. I worked out of town so it got past me, I should have known as the tire guy said that will stop, sometimes you get burned by hiring out, as this should never have happened, given there's been no problems with tires I've mounted and loaded myself. I get my tubes locally from GCR.
GCR