Personally, one thing I think 4Ed got absolutely and unequivocally right was making there be as many spell/power levels as there were character levels.
Doing otherwise is a regression, IMHO.
I'm inclined to agree with Danny. If you're going to call it a spell *level* it makes sense that would correspond to character levels. If not, call it something else: Spell Circles, Spell Tiers, or something.
If I understand 5e correctly, a caster can prepare a spell at a higher spell level to increase damage...so now you've got character levels, spell levels, and casting levels? Just needlessly confusing things IMHO.
Also, another area where I think 4e was mostly successful was breaking spell effects down according to tier. When I think about spell power my mind tends to clump them into 3 groups, much like 4e's tiers:
Game-players: these spells follow the rules or break them in minor ways (eg. Dimension door, fireball, knock, web, limited invisibility)
Game-changers: these spells break the rules in significant ways and redefine the conflict or challenge facing the PCs (eg. Fly, teleport, pass wall, mass resistance, see invisibility, full invisibility)
Game-makers: these spells break and rewrite the rules in dramatic ways which can have long-lasting or permanent effects (eg. Reverse gravity, wish, earthquake, greater curse)