The ordinary storm is not particularly impressive, but increase adds lightning and kills a few villagers.
My best evil creature reserves the most powerful version to rip down tempels..or cause damage to them.
I remember sometimes, while playing neutral, using the basic Storm on town centers just to cause panic and maybe whip some of the whiny villagers up into air. Plus, it had the satisfying "wrath of the almighty feel" with a fairly low prayer point cost.
Indeed that the rain storm doesn't do anything but it is used for impressing villages well at least the normal one is harmless...because the others can cause damage.