Hmmmm, you want reasons?
The Tyros has an edge in key feel.
the 2100 has speakers.
The Tyros has a hard drive option.
The 2100 has speakers.
The Tyros has a great screen.
The 2100 has ....well you get the idea!

As for the kn7000. My initial hangup was the fingering mode, but I may be past that now. The Yammy has forced me to buddy-up with AI mode. Maybe the 7000 will play that way too?The harmonizer really does bug me, because there are occasions that I do not bring my rack, and I still need to have quality mic effects and EQ. The mic is #1 priority in my shows, then the drums, then the bass, piano and all the rest.
The kn7000 may still find it's way into my studio...who knows.
(Down Doug...down boy !)