Totally agree with all of you who said always use a lens hood... it can only help but never hurt. The main purpose is to block light that is outside the FoV of the the lens (i.e. not supposed to be part of your image but might enter the lens and degrade IQ (particularly reducing contrast). The added benefit is the excellent protection it offers in the event the lens is bumped, banged, bonked, or dropped.
As for the comments about using filters to reduce flare or not needing a hood because you use filters... I don't think that's correct... filters tend to increase flare. CPL filters will reduce reflections from surfaces such as glass or water that are in your FoV but that has nothing to do with what a hood does.... the hood blocks light rays that are outside the FoV.