I said "Harm" because there was not an option "Maximize suck, Empower is the way to go !".
Plus, once you're a greater deity, all your spells are automatically maximized, so you'll be screwed if you've taken this useless feat ! On the other hand, a greater god's empowered fireball would deal 90 damage -- just the absolute maximum, even for the extra damage from Empower !
OK, you don't think you'll play a greater deity so you don't care about this argument.
Yet, Empower is better. It's just a question of statistics -- and actually, the smaller the dice, the better Empower is. If you have a spell that deals d12s of damage, Maximize will be better than the average Empower result. If you have a spell that deals d4s of damage, the average Empower result will be better than Maximize.
"How that ?" Will you say. "A maximized d4 is 4, while the average of 1d4 is 2.5, multiplied by 1.5 this is 3.75 and inferior to 4 ?"
Yes. But with d4, you pay this 0.25 extra by one spell slot one level higher. And that's not at your advantage. With d12, the average empowered result is 9.75, and that extra slot level gives you 2.25 more per die -- something more valuable.
I once made lots of calculations on that and found out that Empower was better for all d6 and smaller spells, roughly equivalent for d8 spells, and worse for d10 or better spells. Since most spells use d6 anyways, Empower is better if you believe me.
Also, the more dice you have, the better Maximize is... But to make me convinced to prefer Maximize to Empower, you should have a whole different scale to spells, with things like a 1st-level spell doing 5 times the level damage in d10... That would need, to be balanced, to completely change the scale of the hit point system in D&D (people would have thousands of them !).
As it actually is, the level at which a maximized spell is statistically always better than an empowered one because of the sheer amount of rolled dice, is the level where you play a greater god.
Note that if Empower was a +3 levels feats and Maximize a +4 levels one, Maximize would probably be better (but then you'll need to have twin spell and energy admixture at level +6).
On the other hand, if Empower was +1 level and Maximize +2 level, Maximize would be the absolute worst most sucky feat ever, to take only for flavor if you have a sort of manic-obsessive lawful wizard (for the regularity factor).
Finally, you can empower twice a spell and thus double its efficiency for a +4 level cost. Triple it for a +8 level cost. Even if the more you apply a feat, the least useful it becomes (compared to a normal spell of that level, extreme example the empowered 4 times Magic Missile dealing (5d4+1)×3 damage compared to Meteor Swarm), it's always nice to be able to stack use of a metamagic feat. 'Cause if you maximize twice a spell, that's exactly like if you empower it only once...
And don't make me started on Energy Substitution (Sonic) ! I've met more trolls (vulnerable only to fire and acid) than fire giant (immune to fire) ! And that sonicball will not be extraordinarily efficient against, say, a mummy or a frost worm. Lots of creatures have fire or cold or acid or electricity resistance, but lots of creatures also have a vulnerability to one of these. Few creatures are immune to the sonic energy (in the MM, only the Destrachan); but few also are especially vulnerable to it (in the MM, only the Yrthak).