If size of cut didn’t matter (not in a confined area), wouldn’t a thicker cutoff wheel last longer? I was comparing mainly between a 1/16 and 1/8 width wheel. I was trying to compare between cutoff wheels that you can get at Harbour Freight vs what you would buy at big box home improvement stores. Also, do the diamond cutoff wheels work that much better than masonary wheels?
Cutting disks should be thin. Grinding disks are thicker. Thicker disks means removing more material, which takes more time. Typical disks in Europe is 1mm thick, and I'd categorize a 1/8" (3.7mm) as a hybrid, usable for both cutting and grinding, but not excellent at either.
A thinner disk also leads to less heating in the material cut, as less energy is deposited.
In addition the disk should be made for the material you're working with. Different materials behave differently.
It depends what you are cutting. A metal disk will out preform with metal. a metal cut off disk is a good recipe for an injury with masonry. Are diamond blades worth the cost I use them when I need a very clean cut with not much damage next to the area being cut. Diamond blades also are usually coated on a metal disk so they do not fly apart like a fiber blade. I have 1/2 a dozen different blade types and thicknesses as there is really no true universal disk, or blade for a grinder when considering both cutting and grinding both metal and masonry.
It isn't that the diamond blades have a longer rating on them. It is that they provide a cleaner cut.
If I am cutting rebar I get the cheapest blades possible and they last 4-6 cuts. If I get something 10 times more expensive they last 6-10 cuts.
If I am cutting tile I go with a diamond blade to get a smoother cut and less cracking chance (vibration means more chance to crack). I will get a thinner disc for tile (thicker for stone).
If I am cutting granite or other stone I go diamond to lessen chance of chipping.
If I am cutting off things that don't belong or cutting weird stuff like backer board I generally use a cheap metal disk. On my metal disks I get thicker because they last longer and I don't need to be exact.
I would also agree with most here on HF is not the ideal place to buy an angle grinder. I have tried their tools and like all of their cheap power tools the number one issue is the shutoff not working right. The last thing you need in an angle grinder is, your a stuck on a cut and the wheel won't stop spinning when you release.