For the large majority of driving PHEVs are superior. They offer identical efficiency for short (<50 mile) trips at a large cost savings. They can handle longish trips where a BEV would wind up dead on the side of the road. Even in the rare circumstances where BEVs are better the advantages are slight.
There are downsides: extra weight of a gas engine, more mechanical complexity, and weird maintenance, especially if its an gas engine your not using very often. The person I know who has one went a couple months without using much gas. Does gas go bad?
