There is one uncommon advantage (or used to be: I hear AF overhauled the system, so YMMV) with FB: the higher your tier, the more miles you accrue for the same flight, in the same class.
I traveled every 6 weeks HKG<>BOD for three years. When I started doing this, I was a so-called "Ivory" member, ie the lowest rank. I watched my account jump up and up and up, and became (again) Platinum within a year. This is when I realized that my flights were not credited with the same number of miles, even though they were always the same, booked by the same agency, under the same class. Every time I went up a tier, I got a bigger multiplier for my miles, separate from the multiplier you get when flying Business or First. Flying as a Gold member gave me, if memory serves, 125% of the actual mileage, and Platinum 150%. So I reached a point where flying HKG<>BOD in Business class as a Platinum member got me 22,000+ miles per return flight.
I haven't flown yet with another airline that does that. Also, the thresholds were lower for overseas residents (ie not living in France). I remember the number of qualifying miles for Platinum was 70,000 for overseas residents, and 90,000 for residents in France. That was quite uncommon too. Not sure whether this is still trues with the new system.