Well the big advantage of PWM fans is that if you've got good PWM control you should be able to run them at very low speeds (600-700rpm) for near silent operation without motor buzzing (often caused by under volting the motor)
Remember you generally need 4pin headers on you motherboard to use them.
While some of the very expensive fan controllers (we're talking £100+ range) work by pwm on a 3pin fan I've never seen it done on a motherboard because of all the additional power regulation that's needed.
3pin Fan headers on motherboards (and the vast majority of fan controllers) are controlled via voltage reduction not PWM so there is no point getting a 4pin PWM fan if you are connecting the fan to a 3pin header.
My choice would probably be the Viper, While I cannot confirm the current Apache and viper, the original Apache was made by Scythe and used the same great Fluid Dynamic Bearing as was used on the old S-Flex line.
Side note sycthe also make some fans for Gelid and Thermalright (depending on model)
Not sure on the Arctic F14 PWM, the 120mm version is good for a cheaper fan but the 140mm is a very different fan not the same fan scaled up.
The Thermalright
TY-140 is supposed to be good
http://www.scan.co.uk/products/140mm...ssion-fan-blad and there's a higher speed version in the TY143
http://www.scan.co.uk/products/140mm...45-db-case-fan
Note, these do have 120mm fan mounting holes not 140mm so may or may not fit, depending on the case and hole placement