I bought several of these for the Edge Apex Pro, some smaller stones (some of these combination stones with the chinese #3000 "ruby whetstone") as dressing stones and some benchstones.
The Edge Pro format (i believe the #1500 is some kind of boroncarbide variant as well) comes well trued and is a good performer if your grinding surface is small. So scandi and flat grinds are a no-go. These stones perform well up to the highest imaginable pressures, they stay flat a very long time and if they feel dull you dress them with a coarse siliconcarbide stone.
The benchstones are a mystery for me. The #800 is hard like a dressing stone for grinding wheels, the #1500 is still harder than every stone in that grid rating i've ever seen. Every standard 1000 King or comparable gives you more performance for simple knife sharpening. I bought these as dressing and flattening stones for harder fine stones. They give a better surface condition than siliconcarbide stones. I have the DMT #800 and the #1500 boroncarbide benchstone, but other than stone maintenance they are of little use for me. I have used them to smooth the surface of a Spyderco ceramics fine benchstone i trued. The #1500 with oil will do a good job for refinement of the surface. My best guess is that a translucent arkansas will benefit as well of that tratment. But i like the smaller stones of 5x2 cm and 10x2,5 cm more for this task. In my view these are very versatile for stone maintenance.
Since there were a lot more and far larger stones in boroncarbide available half a year ago, my best guess is the big ones were a novelty that will slowly vanish. Siliconcarbide is cheaper and there is plenty of experience in the industry how to use that for a grinding stone. I think the large boroncarbide blocks are used in manufacturing together with finer grinding compound as a high performance grinding solution. So maybe you could true and polish your chisels and other hard tools in one go with the matching polishing paste?
some people not gonna spend $2-400 on stones, if you rather spend that much on knife, I would just get some cheap one from ebay, it will still sharpen the knife, may not be as quick as shapton glass etc. you could also buy 1-2 pc cost you about $5 and give it a try.