This is how I see the game, heavily influenced by excellent posts by others. Here is my (very) simplified spectrum of the 4 resources...
Bursts (attack spell or heal spell or push damage) = life
Persistent Threats (creatures) = attack actions, life
Spell Sources (spawnpoint / familiar) = spell actions, channeling
Mana Advantages (inc. mana siphon) = channeling
Every mage build has an anticipated game length for victory. This varies from Lord of Fire (shortest) to Mana Denial (longest). The shorter the remaining game length in your strategy, the more you value the top of the list. The longer the remaining game length in your strategy, the more you value the bottom of the list. So Mana Advantage is early game and Burst (when not removing Persistent Threats) end game.
However, the opposing mage usually has a different game length in mind. This is where you have to be flexible and not get too far behind the opponent's spectrum of the strategy. The control player will trade life resource to gain control but may "fly too close to the sun" and get burnt. Surprise damage spikes is key here as a control player is relying on abilities like regen to undo anticipated damage then suddenly he is lower than expected and reacting to the aggro schedule.
I think that any point during the game, one player dictates the schedule and the other is reacting. This is initially the more aggressive more short-term build but if a less aggressive more long-term build weathers the storm, he will "take control", even if not playing a control build. For example, a mid-range aggro build vs. an all-out aggro build: given time, the former will "take control" via mid-range mana advantage.
Here is a hypothetical tempo-based triangle...
Super Aggro > Pure Control (former too fast for latter to gain control in time)
Mid Range > Super Aggro (former strong enough to resist then leverage advantage)
Pure Control > Mid Range (former given enough time to gain control)
">" means "has an advantage over" so that the match-up if equal skill and luck is not 50:50
If we assume the above hypothetical triangle is true, the trick is to morph your play tempo to become the speed that has an advantage over your opponent. I'm not saying the triangle is true, just demonstrating my theory of how being flexible and changing your strategy's tempo is crucial. Which is where I see channeling vs. damage is all about.
