One nice benefit of CurveLabels is the direct labeling of each series with the name of the group. Using this instead of a legend reduces the amount of eye movement necessary to determine which curve represents which data. Direct labeling facilitates faster decoding of the data presented in the graph.

Clearly, there are use cases where direct labeling may not be feasible, in which case a legend is needed. In such cases, placing the legend as close to the data as possible (reduce eye movement) would be preferred.