Between this 3 bikes: KTM duke 690, ducati monster 696, yamaha FZ6 naked bike? which 1 will be more dependable?

I'll go along with most of the people (Yammy, KTM, Duc), but also point out that even more important is the dealer. Which of the dealers is most honest, most reliable, and most reasonable. Talk to bikers in your area - most will be pretty vocal about their experience with their dealer.