The advantage of the cv is that it is unitless. This allows
coefficient of variation to be compared to each other in ways
that other measures, like standard deviations or root mean
squared residuals, cannot be.
“It is interesting to note the differences between a model's CV
and R-squared values. Both are unitless measures that are indicative
of model fit, but they define model fit in two different ways: CV
evaluates the relative closeness of the predictions to the actual
values while R-squared evaluates how much of the variability in the
actual values is explained by the model.”
(source: UCLA-FAQ)