Everyone will have personal preferences with fans. They all behave slightly differently depending on how they are used too. Some fans are noticibly noisier pushing air than pulling it for example. Some fans whine / produce noise at certain frequencies when undervolted etc. Basically among "high quality" fans at least - it is a very horses for courses affair.
That said I will give you my personal opinion of the fans I have tried.
1. Akasa Apache black - I have only used these as case fans so cannot comment on effectiveness on a heatsink / radiator. They are very quiet when undervolted but distinctly average in volume when running at 12v.
2. Noctua NF F12 - Tried these as radiator fans. Performed well - more or less the same as my scythe GT's but there was something about the noise they made I couldn't get on with personally. I ended up swapping them out for P12s which I was much happier with.
3. Noctua NF P12 - I have used these as both radiator and case fans. Of all the fans I have ever used I would rank these as the "all rounders". They are not the absolute top performers - but they do pretty well, usually remaining within a couple of degrees of anything else. They are quieter than most other fans running at an equivalent RPM - and they are consistently, comparatively, quiet regardless of airflow restriction.
4. Scythe GT AP14s + AP15s - Used as both case and radiator fans. I must admit - nothing beats these for outright performance in scenarios with restricted airflow. That said there are better options for case fans - though they are designed with static pressure in mind so that is not surprising. On average they perform a little better than the Noctua P12s. Noise wise I would say they produce slightly more - but it is a different "type of noise". If I was after the quietest possible build I would still give the edge to the noctuas I think.
5. Aerocool Dead Silence 120mm - Used as both case and radiator fans. When undervolted, these really live up to their name. At 5v they are the closest to inaudible I have heard in any application. At 12v in free air they are very quiet but on a radiator / heatsink the P12 is quieter and performs slightly better at the same RPM though that may just have been my ambient temps varying.
Off hand I don't know which of those I have mentioned come in PWM flavour. At any rate those are my opinions on various fans I have tried which are reputed to be quiet.