In DVD-R, address information is communicated through microscopic pits located just outside of the groove that carries the data. Now, the problem with this approach is that the laser has to write data onto the groove and read the address information located outside the groove, at the same time. Proponents of DVD+R claim this address system creates disturbances in the writing process and results in more errors.
So in DVD+R, address information is encoded in the shape of the groove itself. It is argued that this system minimizes errors, and makes address information easier to read, especially at higher writing speeds.