I am happy using Kemper but I sometimes find that the profiles don't quite capture the bass frequencies (around and below 100Hz) of the original amp+cab+mic -combination. The way I hear this is that the profile seems to be lacking the depth or punch of the real rig that it is profiling.
Here is a little test I made with Match Eq. It is more or less along the lines of the tests that I have made previously: After 90Hz there is a few dB bass roll-off. In this case it is quite mild. In some other cases it has been more noticeable.
In the first picture is a Mesa amp loaded down with Torpedo Live with an IR versus Kemper profile of the same rig. The eq curve shows the frequency response of Kemper vs. the original. The original would in this case be the straight 0dB line.
In the second picture is Mesa loaded down with Torpedo Live, without an IR ( a di signal) and a di profile of the same setup. It seem that the bass roll-off isn't present in the di profile, but in the profile with the cab, although there are some other differences (for example a dip around the 250Hz area).
I refined these profiles with seven string guitar playing low muted power chords and also open chords.
I used a looper pedal in front of Mesa/Kpa in which I had played riffs and single note lines. So no test signal of sine sweep or such.
I would like to add that I am not trying to argue about anything, just trying to visualise what I am hearing and perhaps have some exchange of thoughts on this subject.
Furthermore I am aware that in a mixing process a hi-pass is often applied much higher than where these differences are.