Don't forget damage type. Sneak attack damage is of the same type as the weapon that makes the attack.
So, a rogue with chill touch, eldritch blast, fire bolt, and/or ray of frost (I know they're from different spell lists, but feasible through feats/multiclassing), can deal several d6 of sneak attack damage of the necrotic, force, fire, or cold types. And switch between them whenever they want.
I don't think the extra die or two of the cantrip matters, but the sneak attack damage type does. And that's if you've already house-ruled to allow cantrips. If you open it up to any "ranged spell attack," then your rogue cam essentially select from any damage type, any time.