Based on a quick skim of Kanata's documentation, it does not appear to be context aware, e.g. have different mappings based on the application or device. This is of course a matter of preference, but I find Keymapper's configuration format more straightforward. It doesn't try to mimic QMK & friends. Rather than layers it has contexts. The concepts are similar but unlike layers, you can multiple context active at a time. Keymapper is really flexible. Pretty much your imagination and willingness to tweak stuff is the limit.