Just an observation from someone who has used various amps sims etc for 2 decades now. The one thing that sets the Kemper apart for myself and this is purely my experience is that. With the Kemper, I am far more aware of of my guitar choices and string selection. I have a style of my own for good or for worse, when I comes to guitar playing and previously, I could achieve most of what I was after with pretty much, any guitar I chose to use on any given day until I bought a Kemper. With the Kemper I have become acutely aware of "That part needs a Tele/Strat/Les Pau/Etc whereas previously, I had always been able to mug it using often guitars that are in themselves somewhat generic in tone. I even went so far as to trader in my "Pointy Headstock Strat Style guitar, for a Telecaster because for me, good as it was, it was exposed by the Kemper as being, great as an all rounder however, really only shining as a box of lead tricks and as, lead is not truly my forte, it became relegated to the "not quite there category".
I used to be somewhat wary of those gear nerd articles in which some guitarist would talk about how many amps they dragged into the studio and how many guitars they went through to achieve a certain tone. It struck me that, there was a certain degree of; "Well, I have the budget and the amps on tap so why not try them all and that, one can become lost when that old amp you used for years did it all. That is, one becomes almost pampered above a certain level and maybe, we lose some focus on what we really were all about in the first place?
I should point out that, I am not a typical "Hi-gain" type of player, my guitar sounds are drawn from a wide palate the song dictating the sound rather than my songs being written from a certain sort of sound. That's where the Kemper hits the mark for me. Each of my guitars unique voicing is now totally apparent and I'm now far more critical of what strings with what guitar I use. In short, my experience is now akin to that of many guitarists who unlike most of us, had the opportunity to try any number of amp and cab combos when recording.
The other thing I've noticed with the Kemper is that, layering is far easier, the different profiles don't tread on each other's feet sonically as it were, in the same way that other units have done. I've had 5 years with my Kemper now and my experience is that, the biggest problem I have these days are my now cack handed efforts at guitar playing, not the "amp(s) and guitars I'm using.