You can compare the technical data yourself by looking in the manual.
With the two old converters from back then, there won't be much difference, as both units use converters that were available at the time.
BBF and MF II (not I), for example, have the same converter latency of 44 / 28 samples A/D, D/A at single speed. The rest of the technical data will probably match as well.
But the technical data alone do not provide any information about the sound, you would have to work that out for yourself in listening tests.
But what significant differences do you expect?
When comparing current transducers, the differences are subtle anyway, that may have been the case back then.
If you ask me whether you should get the new BBF Pro FS, I would rather say that it could (COULD, to be tested!) make a small audible difference.
Just in terms of routing audio on the BBF Pro FS itself, the latency of the converters is very low at 5/7 samples A/D, D/A at single speed. There has been facelifting in many areas between BBF and BBF Pro significantly and also between BBF Pro and BBF Pro FS.
UFX+, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1650v4, Win10Pro22H2, Cub12Pro