Wow, there's a lot of opinions on this topic. I own both bikes; each has it's advantages.
I have a 2009 C14: no flies, AreaP full system, PC3 with Fuel Moto map. I have never used the bags: a 20 pound saving.
My Ninja 1000 is a 2011 stocker, with MRA double bubble screen and 190/55 BT016.
I love both bikes.
The C14 has the tire pressure monitoring system, no maintenance shaft drive, and ABS. Really good features! I also have Pilot Road 2s to enhance handling, plus a ZX-14 seat to lower the seat height an inch. All good.
Both bikes handle really well in the twisties.
Based on testing (racing!) with my friends bikes, the MODDED C14 is definitely faster. However, stock to stock, my opinion is that the NinjaK would be faster.
Really, both bikes are great. If you want a FAST sport/TOURER, the C14 would be your choice. If you want a one-up sportbike, with a great powerband and excellent handling, the Ninja fits the bill.
Stock, the C14 is really restricted at low rpms, while the Ninja is not. Pull the flies on the C14, add a PC, and the the bike pulls like a locomotive down low.
Have fun,
Dave
Bradenton Florida