Sonic,
The Yate Loons are basically the same as the Nexus fans. The Nexus are quieter because they use a dropping resistor to slow the fans. Using a fan controller, you can turn your $3. Y-L into a Nexus... The Y-Ls I have here are quiet enough for me without any controller, but the noise nazis are never satisfied. So the Yate Loons are quiet but they aren't great fans. The Sanyo Denki 120x38mm fans that petrastechshop and thermalfx (and I) sell when they have some are great fans. Delta fans are top quality. But generally they do require a fan controller as at normal speed they move a ton of air and are a bit noisy. Crank them down a bit and they get good and quiet. Most of the S-Ds I've tested will run from below 5V to above 13V, so you can adjust for just the combo of airflow and noise you want. Also sleeve bearing fans like the Y-L work best in the vertical orientation while ball-bearing fans work OK in either vert or horiz orientation.
So there is no one best fan, just the best one for your specific application. Read some of the fan threads here and you'll get an education.
.bh.