Hi, I have a choice in both, I think 12v would be better though, more airflow.
At the minute i have a fan wired up to 6v, it has 4 leads built in, these are drawing so much power that you can get away with removing the resistors and 1 led, at present, there is just enough power to run the fan, if I stop the fan, it cannot start again on its own lol but
That single led that left on the board is flashing, I i stop the fan, the led either goes out or stays on, but it's no longer flashing and its bright enough to dazzle you I will do a quick video to show what I mean, I feel i can remove one or two of the leads off the fan ad that would give the fan more power..... I'm gonna end up killin me self lol