Further to my earlier comments in a blog post yesterday, I have received several comments about both rigs. The general view remains that the performance of the KX3 exceeds that of the FT817ND although it is in many ways less suited to field use than the FT817.
I have never owned owned a KX3 as these are very expensive in the UK. I own both a very old FT817 and a recent FT817ND. For the modes I use mostly, the FT817s do a great job. I just wish Elecraft radios were not so expensive and looked, and were, more robust. I for one would think twice about using an expensive KX3 as a field radio. I am sure they work really well, but they look flimsy. A fully loaded KX3 is currently more than twice the cost of the FT817, which is a fine radio. My FT817 gets used from MF (with my homebrew transverter) all the way to 70cms. The FT817 has worked all over the world, including indoor handheld SSB QSOs with the USA.
For the avoidance of any doubt I love the FT817 radios and would like a KX3 for home use, if the latter was less expensive. My views, others may not agree.