I see that Karbowanec launched in May 2016 as a fork from the Cryptonote source code. How is it different from Monero, which is also a Cryptonote coin?
Both CLI and QT wallets are forks of CN reference implementations. By skimming over the Github pages, it seems like there are just some minor adjustments done to the original CN implementation, and that's about it. Also, their website doesn't state any specific features which would differentiate it from CN.
The difference between Monero and Karbowanec is practically the same as the difference between Monero and CN.
Since 2014, and at the time of this writing, Monero had 2866 commits on Github so it's hard to point a finger at some specific difference as there have been thousands of lines of code edited and decades of man-years spent working on it since the inception.