Okay, let's count and compare:
1. Hide, Shield vs. Thirst, Curse, Misfortune. I would choose the first two.
2. Slow – there are no analogs in fire. In my opinion, it's the most important low-level spell; it's no coincidence that it was moved to the 2nd tier in WoG.
3. Wall of Fire – a plus for fire. Provided that Moon is available.
4. Wave, Sandstorm, Force Field – Blindness, Minefield. Fire is also preferable here, although Wave can decide the outcome of the game.
5. Resurrect Living and Undead vs. Sacrifice. IMHO, these are incomparable.
6. Fire Shield, Execution, Frenzy – there are no analogs in earth, but I haven't seen the first two used in online games.
7. Meteor vs. Fireball and Inferno. This is a matter of personal preference. I like Meteor more.
8. Berserk – a top-tier spell, but: it's best to have fire expertise for it. But here's the problem: people usually give up fire to get earth.
9. Implosion and Armageddon. It's incorrect to compare them, but I'll still put them side by side; both are deadly spells.
10. Antimagic. No comment.
11. Earthquake – not often used, but sometimes it comes in very handy, especially for the computer when attacking.

And now, let's add Portal and Scouting here, assign a score from 1 to 3 based on the degree of importance, and each person calculates which element has more points based on their personal preferences.
I got a very significant advantage, and I would give 4-5 points for Teleport.

And water is not even worth discussing – it's the most useless school of magic in SoD.