I have the Ohmura 150 for grinding (great stone, but wears fast!), the EP 220 + 400 and the entire Chosera stone set.
I gotta say that the EP stones work very well for their grit level, although that grit-scale is different from Chosera's.
I just mean that the EP stones work great too and that there is nothing wrong with them.
The Ohmura 150 stone is truly awesome and grinds metal like butter, but it is VERY hard to flatten on sandpaper and it wear super-fast.
After fixing a slightly chipped chef's knife I could already see a clear concavity on the stone; so, it is expensive and short-lived, but very, very good.