PSU; 3 Fans, 2 Fans, or 1 Fan?

I never really thought about this till now. I see some PSU's have one large fan, and some PSU's have two smaller fans. Even same brand and same wattage ratings (give or take +/- 10%), have different fan set up.

I always preferred PSU's with 2 or even 3 fans, thinking that more fans will be better for case cooling. But does a 1 fan PSU just as good or better at cooling your case?

Thanks.

Fan in psu is there to cool psu and not your case.

As goes for psu and case cooling, whatever solutiong moves the most amount of air will probably cool the best.

Right, its there to cool the PSU, but it also helps to cool the case as well.

Well..hmm.
I guess a 1 large 120mm fan moves more air. so that would be a better choice. Plus i always replaced my PSU fans.

Ok, i think i got it now.

The biggest difference, IMHO, is that larger fans tend to be quieter for the amount of air moved.

No conclusive experiments have been performed AFAIK. A lot depends on how well the secondary side is cooled. If it has a clear air throughway, an 80mm would suffice. My Zippy is a single 80mm design and so was the Server-grade Supermicro PWS-0056 I owned. A larger or more fans are not necesary if the thermal design is optimized/the unit is energy efficient.