I've never had an Olight I3E EOS but I have had several ITP A3 EOS which I like very much and look to be quite similar. I prefer the flat tail on the K3, the more aggressive textured shell (making it easier to operate with one hand) and the higher brightness. So in my mind definitely an upgrade.
I also recently discovered that if you twist on and off and on quickly, like within a half of second, it will go into strobe mode, which is something I have only rarely used and had previously thought it had something to do with cycling through the modes a few times
, but in my mind is a great way to "bury" the strobe in a fashion that is quick to access if you do need it.