It's CBN, not true diamond so a bit different, but it was made by Diamond Wheel Inc. Diamond would be for carbide chains. CBN is almost as hard, but doesn't load up like diamond. Honestly the list of reasons is pretty long.
1: It cuts far more smoothly for one. It's similar to using a more slow cutting/"finish grade" file vs a very rough or aggressive round file. If you've ever tried a Pferd File vs a Save Edge, you know what I mean.
2: It doesn't heat the tooth nearly as much, or as quickly as the bonded wheels do. The bonded wheels don't really absorb heat, transferring most of the friction heat into the tooth, which is why it's very easy to blue the leading edge, changing the temper. The CBN wheel (from Diamond wheel INC), absorbs much of the heat. If you're barely touching the cutters up, you may not notice much. If however, you're taking off a bit more not hogging it out, but enough to actually work it a bit), it's far more forgiving.
3: the CBN wheels don't wear nearly as quickly or as drastically as the bonded wheels do, all but eliminating the need for re-shaping. you might have to clean it, occasionally, but that's about it. Plus the mileage - given the number of chains I've sharpened with the wheel for 3/4 and .404, and it's current condition, i'm guessing that it'll last at least 4-5x times as long as the various bonded wheels that I've seen. It's a long-term const benefit, but that's more dollars towards another saw, gun, or bike.
4: The CBN wheels don't spark like the bonded wheels (see above) or possess the potential for coming apart like a bouncing betty. I like my eyeballs free of grinding wheel. Also, my MAXX has a head tilt angle indicator on the vertical base of the unit, precisely where the sparks, and resulting slag formation occurs from the bonded wheels grinding themselves down. The CBN doesn't do this, thus leaving my indicator unscathed and actually legible.
5. Consistency - Given that they don't wear anything like the bonded wheel, the CBN wheel makes more consistent grinds. Each time you re-shape, your re-adjusting the angles slightly, and you're reshaping somewhat differently. It may be within Yankee stadium, but I like having the same profile (within a thousandth or so) every time.
Lastly, and this is minor, but it matters. It seems a bit quieter. This may sound dumb, but I find the bonded wheels much louder, and higher pitched than the CBN. If my Wife or kids are trying to have a conversation with me while grinding, the CBN is doable. Not so much for the bonded ones.
Others results may vary, but that's what I've observed using both Oregon and Molmab wheels. I can't speak for the Dynasaw wheels, but I might try the dynasaw for .325, just to see how it compares to the Diamond Wheel Inc. You can get them off of Bailey's, and maybe Madsen's, but it's cheaper going direct to Diamond wheel by $20-30. Hopefully that wasn't too long winded!