Unupped is far worse than the upped, for the opponent will likely not have creatures of the same element. Maybe splash (loosely using 'splash' here) into a rainbow, so you can kill any element?
Not sure I understand what you mean by splash into a rainbow.
Also, don't forget there are plenty of ways to copy opponents creatures, or create some of your own. Fate egg, mutation, duality on sanctuary, parallel universe, fractal, steal creature creators like graveyard, or not to mention rainbow decks carry many types of creatures more often than not.
Also, upgraded card removes all of your quanta. Unupped doesn't.
Maybe I change it so perhaps unupped kills all creatures of you or your opponent's elemental marks, and drains all of your quanta, and maybe the upgraded lets you pick the element of any creature on the field, kill all creatures of that element, then drain all quanta (or maybe give quanta to your opponent).
There are so many ways it could go.