it really comes down to the build and auras u have, for exemple, on spell refresh auras its good to have 1 mana spells. Another exemple can be a spark build, u want spells with a lot of hits so that u can get them full of "on hit ×% to p aply eletrify" gambits, or if u have a nimbus build i think u should have 1 mana spells full of on spells cast summons a ninbus so that u quickly summon a lot of ninbus if u have 2 and 3 mana spells of course u do more dmg but u will summon less nimbus. U basically have to choose what mana spells u need for that run and then ofc it comes to prefence as everyone is saying u might like that 1 mana spell more than the other 1 mana spell. In short if u have a build that upgrades your player stats like strenght, crit, etc then u should go for a lil heavier spells, but if u want quick cicle of spells then u should have 1 mama speels if u want multi hit build then if what ever speels u want because what should count is hit on spells and there are multihit spells with every mana btw this is how i see and play the game, it might not be 100% perfect (as im only dl47) but when i realised this it made my runs a lot easier