I didn't say that a Water-trained Wizard was weak... just that it doesn't have as many effective attack spells as an Earth-trained Wizard would, what with Hurl Boulder in particular. I have just completed my first Wizard book where the Wizard was trained in Water, and over just a few battles, I have found myself hoping for a level 2 attack spell in school sometime in the near future.
The Water-trained Wizard goes about doing things that other Wizards do in slightly different ways. Extra (good) Surging Waves, Geysers, and Acid Balls are added to replace the "heavier" attack spells. He also has no zone attack spell, range three attack spell, "Circle" defensive spell, etc. that I can think of, so instead he likely will have to rely on more creatures and/or spawnpoints than those with other training. Add to this, he likely will use Rusts which can be handy, have extra Dissolves, etc., which modify the Wizard's play a bit.
I'm just saying that if you are talking aggressive vs. passive... different training may affect how you view the Wizard.
I don't know that the mages fit neatly into one line. Though, now I want to make a nice Ven Diagram...
I find it interesting that there is a generally agreed-upon ranks of aggressive vs. passive mages, whereas the book build discussion (solo, few big, swarm, etc.) results in a more "circular" result.