The biggest difference between divine and arcane magic is divine (coming from your god) can be denied you if you are not following the tenants of your religion. Arcane spells will never be denied to the caster (as long as their are known/prepared anyway...).
This is why in AD&D we played clerics and druids did not have to chose their spells. Basically, they were always prepared so you could cast whatever you wanted as needed. Your god's insight will grant you want you want when you want it... just be careful what you ask for!
In terms of 5E, I would have divine spells are selected as needed on the fly, which would make them very different from prepared spells. You could also just say clerics, druid, and paladins "know" all their spells so can cast whatever, whenever.