I have a Rogue 32kg and a pair of Kettlebell King 16kg powder coats. The powder coat on the Rogue is definitely grittier, so much so that in the beginning it was slightly uncomfortable, but within a couple weeks it had smoothed out. I absolutely love the Rogue, it's one of my favorites.
The coating on the Kettlebell Kings is much smoother, however, I find it to be "sticky" in an unpleasant way. It gets better with time, but initially it created a ton of hot spots during use. Also, the coating comes off extremely easily, it is not durable in the slightest meaning of the word. The handles were also skinnier than I was expecting. not bad, just different (this may just be with the 16kg bells).
It's worth noting that Kettlebell Kings has great customer service, and they're just plain fun to deal with. The first bell I bought had a large powder coat clump in the middle of the handle, they sent a replacement free of charge and never asked for the other one back. Also, you can get 5% discount with code "kbfitbritt."