The Tavern

Or the other way around.

Is there any logical reason for this? They are otherwise identical except for the damage type. I can't wrap my head around it.

Time for wild mass guessing:

-One damage type is considered "better" than the other?
-Experience in one school has bigger/more diverse payoff than the other and this is part of some very werid way at attempting to leveling the playing field?
-Something weird about bolts, water and clouds that nobody cares about?
-Something weird about science/realism in crawl?

Obviously none of these apply. I'm really grasping at straws here.

Anyway if I were in your shoes I'd just make them the same.

Probably because a mirror image elemental caster fire/ice is a pretty uninteresting decision, and because IE has freezing cloud.

It used to be the other way around (bolt of cold and throw frost had longer range than bolt of fire and throw flame). I'm partly responsible for the swap.
The idea is that fire magic is the most offensive elemental school, having pretty much nothing but damage spells, whereas air/ice/earth have a lot more defense and utility. So for fire magic to be competitive with the other elements, it should clearly be better at doing damage.
Giving bolt of fire a longer range than bolt of cold is an easy and transparent way to make it better. Making it do more damage isn't transparent (because Crawl doesn't show damage) and making it do something unique isn't easy.

So it was about ice offering more defense/utility after all, huh. Well I'm glad that mystery has been solved.