The IR definitely makes a difference. In this one and the ones I did before, I was trying to match cabs, mics and mic placements as best I could. The ones after, then it's the exact IR just to get even more granular.
Ultimately, you can get an EXACT comparison. Even with the same IR, with the Kemper, you don't know what amp settings were used when the profile was made. There might even be different tubes in tube amps, etc. They both sound so good and offer so many variables to dial in what you like to hear that I can't see being disappointed with either. It comes down to workflow for most people. For me, the other item is in FX and how ridiculously many more the Fractal has. It wins hands down in that department.