Facet versus scale prediction of Big 5 personality
Several studies have been conducted comparing facets versus factor prediction (e.g., Paunonen and Ashton, 2001; Mershon and Gorsuch, 1988; Ashton et al, 1995; Dudley et al, 2006; Ekehammar &amp; Akrami, 2007).

Many of these studies have found substantial incremental prediction of facets over factors. However, there are several potential methodical issues that may potentially arise: (a) overcoming biased estimates of R-square particularly when comparing analyses with facets versus factors where more predictors increases the bias; (b) overcoming issues of multiple comparisons when there are many facets that can be compared to factors; (c) some studies only have small sample sizes. 

By statistical definition, the population r-square for a factor model is less than or equal to the population r-square for a facet model where factors are defined as a linear function of the facets. Nonetheless, I have not yet read any systematic studies that have provided an unbiased estimate of population r-square in factors versus facets. Having read all the above articles, my hypothesis would be that I would expect an increase in r-square of around 5 to 20 percent, but that's just a rough sense. 

References


Ashton, M. C., Jackson, D. N., Paunonen, S. V., Helmes, E., &amp; Rothstein, M. G. (1995). The criterion validity of broad factor scales versus specific facet scales. Journal of Research in Personality, 29(4), 432-442.
Dudley, N. M., Orvis, K. A., Lebiecki, J. E., &amp; Cortina, J. M. (2006). A meta-analytic investigation of conscientiousness in the prediction of job performance: examining the intercorrelations and the incremental validity of narrow traits. Journal of Applied Psychology, 91(1), 40.
Ekehammar, B., &amp; Akrami, N. (2007). Personality and prejudice: From Big Five personality factors to facets. Journal of Personality, 75(5), 899-926.
Mershon, B., &amp; Gorsuch, R. L. (1988). Number of factors in the personality sphere: Does increase in factors increase predictability of real-life criteria?. Journal of Personality and Social Psychology, 55(4), 675.
Paunonen, S. V., &amp; Ashton, M. C. (2001). Big Five factors and facets and the prediction of behavior. Journal of personality and social psychology, 81(3), 524-539.PDF