My Ninja is in addition to the concours 14...and I know Jim did that as well. Actually, you coudl say I followed his lead. I've now checked out, though as he went to an entire 'nother dimension with his BMW. I'd have to rob more banks to try that move.
The two get compared a lot, which is silly. One is a semi-sporting touring bike. The other is a sport bike, for the road, that happens to have some comfort designed into it.
As far as handling, the concours 14 is a wonderful handling bike. Plus, it does not handle much differently with a passenger, luggage and full top box. I actually passed a ninja 1000 in a tight canyon a few weeks after getting my c14. Drawbacks are weight, and comfort..yes comfort. The c14 has an awful seat and silly handlebar position. Once these are corrected, the bike becomes a nice, week long touring bike.
Engine? One is torquey, quick, and the other slightly high strung. The Ninja feels more torquey and responsive. Again, Kawi did all they could to limit the c14 in low end power. Its easy to fix, but needs some help in stock form. Once fixed, it still has power with a more top end bias like a zx14. As far as the shaft goes, its a big whatever. I lube the chain as I check tires...which a person better do anyway.