which one are u comparing?

1) single 12cm fan to 12cm x 2

2) 12cm VS 8cm X 2

12cm perform definately better than two 8cm ... it push more similar airflow at lower spin ... which also mean lower noise .....

1 12cm fan vs 2 12cm fans is hard to judge.... but having two 12cm fan close together perform not as good as having it separated apart for certain distance...... it cool off larger area.....