Mark..I don't think you could find a couple of headsets so diametrically different as a MAVIC and a Stronglight A9. All that they have in common is thatthey are both turned from aluminium alloy!
The A9 is essentially a very light headset that uses two sets of roller bearings housed in tapered nylon housings. In total there must be about thirteen components in it including the four truncated conical hardened steel bearing surface inserts. There was always a tendency for these headsets to rock sightly. Later models such as the ?12 had the races inverted to eliminate the rocking and to support vertical thrust better. This model was also more robust, more monobloc
The MAVIC "Tout Mavic" headset was a monobloc type of construction, made up of only six components as I recall.The bearings, at least in some of them were 1/8" and made of stainless steel...these ran directly in grooves turned in the aluminium upper and lower components. The upper race and lock-nut were machined in one piece; this had a screw operated clamping device incorporated in it. All in all a trouble-free robust piece of kit unless the races were over adjusted...causing severe brinelling of the aluminium bearing faces.
The MAVIC headsets often turn up on Ebay..so it would be worth waiting for one....and for one of their superb sleeve bottom-bracket units.
Norris LockleySettle UK