I hate it when I see this question!
The quietest fan is one which is not running.
Oh! You'd like it to cool as well!
OK, how cool do you want and how thick is the rad? How restrictive is the rad?
You see, when you take a "silent" 120mm fan, the chances are that it has no "pressure". Once directed at the slightest restriction all actual air movement ceases (to a greater or lesser extent).
Take either of the fans and look for the static pressure specification. Can't find one? Neither could I. So, at like 100rpm it achieves 44cfm blah blah in free air! Now try that through a radiator which unless you've got a Thermochill PA??? will effectively stop almost all actual air flow.
Hmm. Wonder how much cooling the fans will achieve?
Now go look for info on the Panaflo L1A.
Very first link Google gave me led me to a US store who quoted: "Max. air pressure: 3.3 mmH2O"
Not actually sure what that means but that's not my point. At least you have a complete set of stats.
Bottom line is that - when all my ranting is said and done - the 38mm deep Panaflo L1A is capable of still pushing air through a radiator while running silently at 7v.
Now now children i only asked a question, play nice please 
