A star type dresser is easier to get a flat face with then a diamond tip.
Softer wheels sort of self sharpen and constantly expose new sharp grit. They are also easier to shape if you need to do that. I've long used Norton, seem OK. I've got a set of daimon "stones" that I like because they stay flatter.
I'm baffled on this being an air tool. Doesn't look at all like an air tool and the link that C-Bag posted shows it as it a 0.9 amp. No matter really. I've had a couple of those. Total crap in my experience. Had the HF version first, then tried one from MSC (that they don't seem to carry any more) hoping it was better... Not...I have and have used that little cutoff grinder for decades. It works good and for really tough stuff is often the goto. But it has many trade offs. It uses a lot of air and needs at least a 30gal compressor and will still run it out in a hurry. It is scary to use as as the cut progresses it wants to bind and those little cutoff blades are thin so they can shatter. And there is the ton of abrasive dust to deal with. I have no idea what other equipment you have but hopefully you have a good vice. If you don’t have other abrasive saws I would consider this:
My best score outside of what came with my machines was a local CL that was liquidating a friends machine shop. There were a couple of collections of lathe bits and they have been very instructive. There is one that has become my main bit on the lathe. The other great thing is they are all high quality old names that will last me for the time I left before the wheels fall off.
Yes, I see that now.
Yeah, that green is not all that attractive and thankfully, it is only the upper half of the housing. Most, if not all, of the working parts of both are metal, but the quality, fit, finish and functioning of the Proxxon is far above the HF and others like it.