The File Geodatabse API is basically a stripped-down version of the ArcObjects code
that supports file geodatabases. If you already have access to ArcObjects it seems
counter-intuitive to use the less-capable implementation (the FDGDB API exists for
those that *don't* have access to ArcObjects).
Direct access to the Access .mdb file used in personal geodatabases has never been
supported by Esri (even though it has, for the most part, worked), so you'd be a step
up in using a supported API to FGDBs, but it isn't clear that there'd be any real benefit
to using FGDBAPI over AO.
- V