One small remark on Abula's comment (& the thread of ca_steve): in the review, the phanteks went down to 200rpm (but these weren't the xp-bk models).
I cant say for sure because i dont own it, but from what i can tell from the review the least they got it down was 560rpms, given that it says in the same picture minimum rpms 209, if you read below says "Fan will run when Fan Power is higher then 25% 560rpms". In some scenarios fanXpert2 which is an algorith can glitch out, thats why i like to see the RPMs that the fan is running not only the % table. My guess is that the fan will run at 560 or higher, the 209 is a glitch, agian i dont own it so idk, and this also doesnt take merit on the fan, as it was one of the best cooling and sounding of all 140s, just pointing out that the 200rpms might not be achievable.
Here is a phantek PWM (not the same as the review), that i did buy and ran on FanXpert2, the lest on the test is 596rpms, but running 630rpms that you can read below on the CPU Fan.
Here is another example on the FanXpert2 on the Antec True quiet 140, where you can see the test fan below that it can be ran at 200rpms.
Either way i think both fans are great, if you need more cooling and willing to take the 500rpms+ go with phantek, and if you want the most quiet 140 and willing to take a little higher temps go with the antec.