If you watch this video by fluff and Sweetwater it gives a pretty good impression of how close it is to an amp. No not exact but good.
This is a good comparison of the QC vs Kemper.
It shows the character of each unit if you listen very carefully. Here I can hear the extra depth in the QC tones.
Each unit imparts their character on the cloned amp tone, or perhaps it’s the A/D D/A ? …Whatever it is, each box has a sound.
To me the QC has a more complex capture ,
The distortion seems to have a more depth and feels / reacts more like the amp.
Some guys may prefer the character of the kemper.. I mean some love the boss metal zone , right?? , especially if it’s what your used to.