Claim: at low level the frost/fire choice depends less on raw damage and more on whether something else is holding aggro on the target. That's the position I'd defend, with a condition attached.
If you're solo or the tank can't reliably lock the pull, frost wins on survivability, not on damage per second. Fire's argument only holds once someone else is holding the enemies reliably, because then you're free to stand and burn without needing your own kit to save you. I haven't checked the merged tree from the mage guide closely enough to say what frost actually offers you in that moment versus fire, so don't take that part as settled, only the aggro condition around it.
So the real variable isn't a static "which tree hits harder," it's whether aggro is guaranteed elsewhere. In a group with a tank who holds well, fire's case gets stronger. In anything looser than that, pugs, open world, undergeared healers, the safer pick pays for itself.
I haven't parsed actual DPS numbers for either build in the merged 54-node tree, so I can't tell you a real gap in damage. Does anyone have measured kill times per tree at low level with and without a dedicated tank holding aggro. That would settle which side of this actually wins, rather than me guessing from first principles.
Worth flagging that any specific numbers here would be beta build 1.60.1.69893 territory and could shift before live.
