The better buy is the Duke 250.
The engine is far more refined. It is also a breeze to ride in the city. I feel the engine on the 250 overcomes all the way to shortcomings of the 200.
The extra bump in power and torque is welcome. The seat is far more comfortable as well. The ergonomics are well suited for city riding. The mileage is decent as well.
The RC however offers a whole different experience, it is more geared towards sport riding and has some of the best manners on the track. On the downside it runs out of steam very quickly and makes you hope it had a bit more power.
If you plan to ride in the city the Duke 250 is your clear choice.