Picking sectors that are underperforming or out-of-favour currently (due to some short term issues) and hence are quoting at cheap valuations (compared to their historical averages) is dicey. Sectors that have been underperforming due to macro or industry specific reasons may not have bottomed out and may have some more downside in store. Hence, margin of safety may not be as high as desired in such cases.
Contra picks are by definition not likely to perform in the near term. Hence they could test the patience of investors who could start questioning their decision if things do not seem turning