It's no surprise that a wood stove did better in that comparison. It's one conversion vs two. It's a perfectly reasonable comparison to make in many circumstances, eg in poorer countries with less well developed electricity infrastructure who still need to transition away from fossil fuels.

From the article:

> This means that if your electric stove is operated by electricity from a biomass power plant -- a fast growing "green" trend nowadays -- the power conversion efficiency is three to four times lower (11-14%) than the authors of the study assume, and thermal efficiency drops to about 5%. This is similar to the thermal efficiency of a neglected open fire, and one-tenth the thermal efficiency of a rocket stove. Likewise, a cookstove which uses coal or gas directly to heat food is much more energy efficient than a cookstove that runs on electricity produced by a coal or gas power plant.

Re: air pollution, they're completely right to point out that cooking itself - regardless of the heat source used - generates tons of indoor air pollution anyway, making the air pollution concern of wood fired stoves not as clear as you'd expect. You should be ventilating all cooking to the outdoors.

> Any biomass stove design with a chimney basically achieves the same. If a chimney is added to an indoor biomass stove, indoor air pollution drops to almost zero.

They're also quite clear that these trade-offs differ for poor vs rich countries:

> Although it's remarkable how the proposed solutions for this energy inefficiency differ for poor and rich countries. In the developing world, the focus is mainly on designing more efficient biomass stoves that produce fewer pollutants. While achieved savings as a result of switching to biogas would be larger, its investment would be 30 times higher compared to the distribution of improved wood cooking stoves.