So far, of the knives I own/have owned, I have not found any folders that clearly out slice my Opinels.
Svord Peasants are quite a bit thicker (even the mini, which I also have), and have lower convex grinds, which makes them not cut as well. My only SAK (farmer) has just about the same spine thickness, it what appears to be a FFG, but its a narrower blade, so its not as slicey.
I had a Case Peanut that was fairly thin and slicey, but the chord of those blades is also quite narrow, so they have to be thin to cut. However, I didn't have an Opinel by the time that I gave that one away, so I can't really say how it compared. And all of my (non kitchen) fixed blades are quite a bit thicker.
The rest of the folders I've used haven't been close. However, I really don't own many folders, so I don't have the best set of knives to compare.
I quite like my Opinels, but don't think of them as anything more than they are.