As you must have read, the FBL series fan is basically the FBA series fan with the "augmented" design licensed from Lemont Aircraft Corporation (LAC), as mentioned in the link to the Lemont's own site you posted Mike.
Panasonic and NMB have lincenced this technology for awhile and have sold them through OEM lines. They have been available from Digikey for awhile.
One current use of augmented fans that is well known in the silent PC community is Millennium Thermal Solutions, http://millennium-thermal.com/
, known for their low-noise Glaciator series of heatsinks/fans designs the heatsink around a augmented fan. They even have a repost of Lemont's white paper on their site.
The noise reduction is mostly from tip-vortex alteration from the ringcage.
If you look at the data from Digikey's catalog, http://info.digikey.com/C022/V5/SectL.pdf
, pp 872, for the 92mm fan, at the low and high CFM, the FBA does slightly better. But! at the middle range of CFM, the FBL is significantly lower dB-A, the best case at ~24 CFM, the FBL is 4 dB-A below the FBA.
If you look at the P-Q curves, the FBA significantly better perfomance in at 0 pressure, as much as 7 CFM more. But under realistic presure, the FBL performs same to much better starting around 1 mmAq and higher. The FBA outperforms the FBL at maximum pressure, but the FBL outpaces the FBA until about 3.5 mmAq. That means, the FBL should do better than FBA in most heatsink applications, but both are lousy under heatsinks that will generate a lot of backpressure(> 3.5 mmAq).
Because of this, most of us use Panaflos for low-pressure applcations, e.g., case fans, which they are well suited for. The question is, for case fans, does FBA or FBL perform better? Well, that depends. If the pressure is less than 1 mmAq, then FBA perform significantly better. Above that, FBL perform much better. I don't know what a typical case fan on a mid-case PC would see. Does anyone know this number?
One last thing: FBL have a disadvantage in clearance over the FBA. Because of the ringcage design, the side of the ring cage needs to be somewhat clear for it to be effective. For this reason, as well as the lower maximum pressure, the FBL would probably do horrible as powersupply fans. Also, to get maximum advantage from the ring cage effect, the fan should be mounted half-in/half-out. Standard cases do not provide this mounting mechanism. As you can see, the augmented fan, FBL series, performance is highly dependent upon the placement in the system.