The Bianchi retention device is very awkward and odd to deactivate or is that activate to release, but you allget the idea. The CQC Serpa is awesome, and the design of the retention lends itself to finger out of the trogger well until it is GO TIME.
I was given a Bianchi as a gift and got rid of it after practicing some presentations with it as the design on paper is nice, but the actual device fails miserably.
IF you are in the market for either I would say go with the CQC Serpa and you will not be displeased. I can draw from concealment with the CQC as quick as I can a non-retention holster. The only problem with the CQC Serpa is that it does stick out a ways and will obviously print unless you are dressed up like some lumberjack up in the Yukon.
In training my wife to present better, the CQC retention device has made the transition to finger along the slide a much easier task, now it is instinctive.