we've demonstrated that there's no real situation where coalfuel is a viable power source. How about this: What's better, geothermal power or forestry biopower gen + biofuel? (not biomass)
They both give 20k eu at 20eu/t, so it depends on availability of biomass and lava.
I do consider both somewhat underpowered, and prefer using forestry biogas engines running on biomass (not fuel) then converting MJ=>EU with one of the crossover addons (currently favorite - transformers)