I can't hear a difference between any of the more distorted profiles. They all sound the same through headphones.
I think Spikey might have a point. I’m not trying to be cheeky are condescending in anyway but either there is something wrong with your Kemper, your headphones or your hearing if all the distorted profiles sound the same. I can definitely hear clear tonal differences between even different profiles of the same amp from the same pack let alone from amp to amp.
My own hearing is “okay” for a 59 year old who has been standing in front of Mesa Boogies and a horn section and right next to a heavy handed drummer all my life but it is far from perfect. I really don’t hear much at all above 11khz (probably one of the main reasons I never find any profiles “fizzy” ?) and what there is in the upper ranges s often obscured by the constant whine of tinnitus ?
You also mentioned that you had the same experience with Axe FX and Guitar Rig 5. Both are excellent products. the Kemper and Ax are generally regarded as the top end of the pro range for this sort of stuff and you are using good quality headphones. Therefore, the only logical conclusions are that either a) your hearing is damaged ( I hope this isn’t the case as hearing damage is permanent and a major loss for any musician) or b) your expectations of how headphones should sound is unrealistic.
I would definitely recommend a hearing test in the first instance; if only to rule out hearing damage.