BR505 disc vs Ultegra 6800 caliper
They're not entirely the same bike (despite the model names). You have to engineer a disc brake fork to be reasonably stronger in some ways than a rim brake fork. 

You probably won't notice a difference in shifting or ergonomics once you get past a certain point (for a lot of people, I'd say this is Tiagra/105; however the psychology of having an ultegra shifter or whatever will make things feel smoother even if they aren't noticably smoother, for some people). The braking will be stronger with the disc brakes, and easier to stop if you ride in wet weather. On the other hand, repairing rim brakes just requires a few hex keys and a few minutes and anyone can do it (vs a hydraulic system).

Really though, you have to try both bikes in the context you'll use them. You may like one better than the other. You also have to think about how teh disc brake and rim brake bikes cost the same -- disc brifters+brakes are more expensive than their rim counterparts, along with the cost of the wheels and stuff. So, where is the rest of the stuff being cut down in price?