The 901 produces less vapor, without question, but it has more flavor though.
The whole thing comes down to the resistance of the atomizer.
The 510 has much lower resistance, which equals more vapor, and more nicotine inhaled.
The 901 has a much higher resistance, which equals less vapor, but often more flavor.
Neither atomizer lasts any longer as far as I know.
And the battery life differences are probably pretty much negligible.
If you are trying to decide between the two atomizers, decide on vapor or flavor.
You can always get more powerful
batteries for either one.