The choices made in this thread indicate preferences in the trade off between Accutance (the appeance of sharpness caused by either a prominent grain structure or by developer action on edges of dark/light areas) or very fine grain (usually caused by solivent developers that erode the grain and fill in areas between grain causing liquid like tonality) Other trade offs are in contrast both local and global.
Format of course plays a large roll in preferences as well. I have used PMK on roll film and found it too coarse for enlargements past 8x10 or sometimes even 5x7. But it is king for my 4x5 film choices. I am rapidly favoring Microdol X for roll film because it really enhances the enlargability. It seems that with TRI X - no matter how soft a developer I use, the grain remains sharp, making up for the accutance lost in the Microdol. For FP4 in roll film, I think maybe split D-23 might be better because it doesn't degrade accutance as badly as the Microdol but it still is fairly solvent and compensating.
I usually try to fit the whole contrast range of the scene on the negative so that it is printable on grade 2 paper without dodging or burning. This of course changes the dynamics of some developers. Microdol, D-76 or PMK for most film is good for 5 stops to meet this criteria. To capture more stops though, will degrade the film speed by as much as 1 stop and will require 15% - 30% less development time. This will usually improve the smoothness of the negative in most developers. But in low light when film speed needs a boost and contrast along with it, pushing will usually cause an increase in grain and that may not be what is desired. This may be photo 101 for most on this group. So where am I going?
Some very famous photographers use one combo for what they shoot and they always shoot the same kind of thing with the same kind of format. This works. But I know that I will mostly use MF for people and LF for anything I can set up for and "cute little films" when camera size is important. All with consideration of how big the print will be.
So I need to keep my choices paired so I will have familiarity and competency with those combinations but I still need the magic bullet for what I do. That is what precipitated this whole thread in the first place. Following this backwards and assuming each in this thread has discovered the best combo for what they photograph, you could almost tell what they shoot by the film and developer they choose.
So I guess the take away here is: Know what you do best and do that much of the time Use the format that is best for that type of shooting (with consideration of the print size) and use the film and developer that give you the grain you prefer in the contrast range you prefer for the print size you prefer.
Did I miss anything?