I have used the MF-14 data back for a place that I worked for. Whilst it is all right, I didn't like the fact that the information was on the frame.
The MF-18 is the only data back for the F3 that imprints between the frames (vertically) other than that it is pretty much the same as the MF-14 and MF-17, these are the three data backs for the F3.
The MF-17 & MF-18 are designed for use with the motor drive MD-4. The reason is that there is a small drop down piece that is designed to come into contact with the two external contacts on the MD-4.
The reasoning behind the Nikon factory making the MD-4 compulsory with the MF-18 data back, is because as the information is fitting between the frames, only the MD-4 will give consistent frame spacing, therefore it was designed that way.
I have the MF-18 and I use the back with and without the MD-4 drive attached. I will always use it in sequential numbering mode when I'm somewhere and need to know the chronological sequence of frames and/or rolls of film. It can also be set to date, but beware when crossing time zones into another day, especially if you travel from Australia to America, they are nearly a whole day behind us.
I have never seen the MF-17 and I believe it can be used with the 250 frame magazine back as well. That said I have used a magazine back on F3 cameras a couple of times and don't remember what kind of back it had as I was too busy trying to take pictures and figure out how to load and unload.
The MF-14 does have an alarm clock which does work. I once set it to ensure I didn't miss a train, as I was dozing at a station.
I only have and use, the MF-18 these days.
Mick.