Which ESR case are you asking about? If you're talking about the Smart Folio knockoff (i.e., the "Rebound" case), I have (or had) both.
- The ESR case doesn't feel as nice as the Apple one in terms of material but that's to be expected. I don't find it bad at all.
- The fit / cut of the case isn't as good and somewhat does bother me. The edges of the Apple Smart Folio pretty closely line up to the edges of the iPad (maybe within 1mm). The ESR extends further out and kind of looks and feels bad but this is a little nitpicky.
- The thing that was a deal breaker for me though was that the Apple case folds back on itself and magnetizes the entire front cover to the back so it's very flat and doesn't move around. The ESR only seems to magnetize at the front edge / flap area and so if you try to type with it folded back, the front cover starts curling.
I think for most people the ESR is fine but I'm a crazy person so I returned it and went with the Apple one.