From a game perspective you have choices:
(1) do you want the cavalry on the table at the start of the game or are you prepared to wait for them to arrive?
(2) do you want a few very good units or a larger number of average units?
(3) how important is converting a marginal win to a decisive win by having more pursuit cavalry?
I prefer my cavalry on at the start, particularly if attacking. It is pretty hard to attack without cavalry on the table, and by the time they arrive you don't have much time left to get across the table and win.
So I tend to go for organic cavalry, which generally gives French the choice of:
Chasseur/Hussars - 4 good units
Polish Lancers - 2 very good large units
One of the other allied cavalry units - mostly poor value
Personally, I prefer more units to less, so take the Chasseur/Hussars, but both are good choices. The Poles are only allowed in a few theatres.
If you are prepared to wait for your reserves, the French generally get to choose:
Cuirassiers - 2 very good large units
Dragoons - 4 good units
Lancers - 4 good units against foot
Since reserves are not on the table for very long, I would personally take Cuirassiers - they can do more damage quickly. Again these choices are not always available in all theatres.
The games I played have not worried about the marginal/decisive wins - so the number of pursuit cavalry has not been important. If that is something of concern, then if you are taking reserve cavalry, Dragoons may be of more interest.
Historically, the different types of cavalry had different (but overlapping) roles. The light cavalry (Chasseurs/Hussars) tended to perform the screening/scouting/pursuing roles on campaign but did form up for battle. The Cuirassiers tended to be kept for battlefield use. Dragoons were in between - they were used for both roles. Light cavalry were smaller men on smaller horses, the Cuirassiers bigger men on bigger horses. But in practice roles were blurred. There are lots of examples of light cavalry being used as shock troops on the battlefield and Cuirassiers being used for screening or pursuit in campaigns.
Cam