I mean it kinda depends on your magic / melee damage, they're both good for healing i prefer darktoad but that's just me. If you want good healing then you should probably get Natures Wrath spellbook sold for 10M by rising waters or from maze.

Thanks,i have more melee bonus.

if tower you would know that rusted coin scythe is OP in certain floors such as floor25 where there are a crowd of mobs and you can hit all of them to get maximum regeneration in just a few seconds, some other floors applies too, but generally you should know that darktoad is the safer option as rusted coin is melee and while using ur special u actually may lose more Hp than gain.