When I bought my brushless 18v makita grinder a couple years back, it came with a Makita branded grinding disc, it's by far the best I've ever used, it's a light brown beigey colour rather than black like most, it seems slightly softer and doesn't skip around on the surface of whatever you're grinding.
I normally use 3" roloc abrasives, but if I ever wanted more hard discs, those are what I'd look for.