There is no question that disc brakes offer a big advantage off-road but there has been much debate if they are needed on road bikes. This debate has been fueled by the UCI’s (pro cycling’s governing body) slow approval of disc brakes on road bikes.
Now that the UCI has approved disc brakes many of the pro teams have made the transition to the technology including Trek Segafredo Pro team which will be stopping with discs at this year’s Tour de France.
The argument against disc brakes goes like this... current brakes work good enough, disc brakes are heavier (about 6 ounces per bike) and they are more expensive. Interestingly this was exactly the same "against" argument used when disc brakes were introduced in Cyclocross 5 years ago. The UCI was slow to approve, some of were slow to adopt, but once racers were winning with disc brakes they became the norm.
If you are considering a new road bike purchase, and are debating whether to get one with disc brakes, perhaps the best way to look at this is from the perspective of which brake system offers best overall system performance.
For that we should examine two other bike technologies / trends that came first that have at influenced the need for disc brakes.
In conclusion if you want to take advantage of full carbon wheels and use a wide range of tire sizes, disc brakes offer the best solution! The new normal!