I thought I'd share my experience with these.
I bought a 5-pack of the Arctic P12 PWM PST's for £33 off Amazon a few days ago for use on a 360 radiator in a custom loop. I was using Corsair LL120's before and although I like the RGB I wanted to see how much difference more optimised fans would make.
I used 30 mins of Deus Ex Mankind Divided as my test just because that's what I'm playing at the moment.
At 1350 RPM under load my maximum GPU temps were 3c lower with the Arctic P12's.
Also 3c difference with 1800 RPM Arctic P12 vs 1700 RPM Corsair LL120.
At the same 39 dBa when using Corsair LL120'[email protected]
I could run the P12's at 1500 RPM which resulted in 4c lower max GPU temps.
~40dBa is my sweetspot for noise/performance.
I measured dBa using my phone in a consistent way with everything active like mechanical hard drives, pump, 3 extra LL120's as case fans at low RPM etc...etc...
So I find the P12's definitely perform better or are quieter than the Corsair LL120 but that was to be expected given how much space the 2 LED loops take up.
I run these at 1500 rpm under load and I'm very happy with them for the price having paid just £6.70 per fan with the 5-pack.
I'll either sell the 2 I have spare or use them on a second radiator in future not sure yet.
The PST daisy-chain feature seems to work well and is handy if you run out of fan headers.
I did encounter a downside however: At maximum speed of 1800 rpm the P12's make a sort of heavy motor sound that comes and goes quickly and is annoying. Not sure how to describe it. It disappears at 1750-1700 rpm and below though so it's easy to avoid without much performance loss.
I've only tested 3 out of my 5 fans but I did test the 3 individually and they all did it. I thought perhaps it was suffering from a bad PWM signal or power issues or something so I tried without the PST daisy-chain feature hooking each one up to a separate header on my Corsair Commander Pro but it didn't change anything. If anyone thinks using my Asus mobo fan headers with bios or software control instead could make a difference I can try it out for them.