As you can see there is a good measurable difference between the two cooler. For both coolers I can not recommend passive cooling. Although the U12 is capable of it I do think the temperature is slightly too high for this processor. Granted non-overclocked the temperature would definitely be a few degrees lower but inside an actual case the ambient temperature is higher also... so no that's not an option for me personally.
A choice in coolers is definitely something you need to consider. Once cooled with a fan the overall difference between the NH-U9 and NH-U12 is very small. So you need to consider which model you find the most attractive. I'd still go for the U12 model personally.
Which fan would I opt for ? Definitely the low-noise fan. You can't even hear it so that's just fantastic cooling performance versus an inaudible environment. The high performance fan however when it's at full rotational speed can clearly be heard and when you look at the performance differential between the two fans there's a 2 maybe 3 degree difference overall, so the high performance fan isn't really making a significant difference. Perhaps if you want to overclock your processor to extensive heights is where the high-output fan will make the difference for sure.
Luckily you have options. I must say that I'm really pleased with the products from Noctua. For now I'll leave the U12 cooler with silent fan on our test system. It's actually working really well and that surely says something about the quality that is being offered here. Other then the sheer size of the product there's nothing negative to report here.
There is something else in favor of the U12 model as well, it's the price. Although these coolers are not exactly cheap at 40-45 EUR the difference between the U9 (45 EUR) and U12 (50 EUR) model is roughly 5 EUR. These are e-tail prices I found here in the Netherlands. So why would you not buy the U12 model then ? I mean unless you need a smaller size cooler to fit your PC the U12 obviously offers slightly better performance.
Oh last but not least, if you bought a Noctua U9 or U12 product in the past and decided to move onwards to socket AM2 then you have an issue. The cooler bracket's will not fit. Lucky for you Noctua will send you a Socket AM2 upgrade kit for free if you mail them. That's classy and fantastic after sales in my eyes.
Noctua NH-U12S and NH-U14S review We test and review the Noctua NH-U12S and NH-U14S CPU coolers. Both coolers have recently been introduced into the channel with kicks performance and versus some really nice airflow OWM controlled fans that are drop-dead silent. Hey, it's Noctua .. so you know it's good, let's check out the review shall we ?
Noctua NH-C14 CPU cooler review In the long line of Noctua CPU coolers they introduced another CPU cooler, tagged with the name NH-C14, the heatpipes bent in a C shape and armed with not one, but two Noctua NF-P14 FLX 140mm fans this product is bound to keep any CPU released to date nicely cooled and chilled.
Noctua NH-D14 review It is called the Noctua NH-D14 premium cooler -- but as I like to call it ... the Big Ben. Noctua had to go back to the drawing board and came up with the NH-D14 premium CPU cooler. It is a six heatpipe dual radiator design to improve both cooling performance and noise levels. Obviously what catches the eyes is that dual radiator uneven design with a 140mm fan sitting smack down in the middle of the cooler.
Noctua NH-U9 and NH-U12 heatpipe coolers A new trend that started over the past two years is heatpipe based cooling. Several advantages directly come to mind as the principle is quite simple. You move heat towards another spot other than the source. That way you can get rid of that heat not directly away from that source, yet effectively can cool it down optimally on location B. This means less resources and effort is needed at the original point of heat. The less resources I'm talking about is a direct active form of heat dissipation e.g. loud fans. More cooling these days equals more noise, and don't we all hate it ?