The marketing of quiet case fans is somewhat deceptive.

[Derek Semeraro]

There is a tradeoff between higher fan speed (for more airflow) and lower fan speed (for silence). A manufacturer can take two nearly identical fans made up of the same parts, have one run at 2000 RPM and the other run at 1000 RPM. The former can be marketed as a performance fan while the latter is marketed as a silent fan even though one is not inherently louder than the other.

If a fan (marketed for silent PC's) is mainly quiet because its locked down to running at a low RPM, then it's not really any quieter than taking a generic fan and lowering the RPM setting. Measuring decibels alone does not provide proper context. A performance to noise ratio is a more accurate metric. A 22 db fan might rank as quieter than a 24 db fan, but what if the 24 db fan has significantly better airflow? If an efficiently designed "quiet" fan at 60% load offers X airflow at Y decibels, and a "performance" fan at 40% load offers X airflow at Y decibels, the marketing doesn't matter because they both do the exact same job.

Low RPM fans can be better in some instances. For 3-pin fans, voltage control is less precise so it may be hard to voltage control a high RPM to a quiet level. For 4-pin fans, some motherboards require a 50-60% minimum fan speed in their BIOS settings options, and half of 1000 RPM is quieter than half of 2000 RPM. Some people don't want to be bothered with SpeedFan, installing a fan controller and some people don't even want to be bothered with PWM in general. Otherwise, there's not really any need to limit the machine's potential performance, since it's possible to make a high RPM fan spin slower but not to make a low RPM fan spin faster.

[Olle P]

It's also important to notice that "quiet" fans typically also lack in ability to build pressure.
If your fans are to pull air through a dust filter you need stronger fans to generate a suitable air flow.

[whispercat]

By stronger, do you mean more RPMs or larger size, or both?

[NeilBlanchard]

Very often, though - the starting voltage of higher RPM fans forces them to run faster at low voltages. So, even when they are as slow as they can go, they can be faster - and louder - than a fan that tops out at a lower RPM.

[Olle P]

By stronger, do you mean more RPMs or larger size, or both?

"Stronger" means "able to build more pressure".
Traditionally "strong" fans are thicker than their weaker equivalents of same diameter, and produce more noise at the same speed.
There are some better designs that are neither thick nor noisy:
* Scythe Gentle Typhoon (no longer in production).
* Noctua NF-P series (P for pressure).
* Noctua NF-A12x25 ("Flex" and "PWM" versions, very quiet and "good enough" in terms of pressure.)
Probably other as well, that I can't recall directly.