Originally Posted by John cox
FOMAPAN 100 is best in the larger formats, where grain is not really a problem very often. In the UK in 8x10 it costs £99.95 for 50 sheets, compared with £124.15 for a box of Ilford FP4 Plus with only 25 sheets in it. It has a distinctive grain but it also has a wide tonal range. It responds very nicely to being developed in a compensating developer such as DiXactol, 510-PYRO, Caffenol, or OBSIDIAN AQUA. If you use roll film then a compensating developer used with a semi-stand regime is almost a must if you want to preserve texture in the highlights.
FOMAPAN 200 is weird. It is never in this world a 200 ISO film. Reciprocity is a source of amazement too. You would be wise to use 100 ISO in your meter... However, it is a film capable of rendering very pleasing tones and again responds very well to compensating developers to preserve highlight texture.
Someone else will have to tell you about FOMAPAN 400 as I haven't used it (yet).
If you really do want to start with one film from the range and you are happy with 120 then FOMAPAN 100, rated at 80 ISO and developed in OBSIDIAN AQUA would be a good choice (and not heavy on your pocket as OBSIDIAN AQUA is diluted 1:500 as standard and is dirt cheap to make up anyway).
The 120 roll film versions are lively and don't lay flat as easily as Ilford film does. If you intend to scan the negatives you ought to make sure you use a holder that has Anti-Newton Ring glasses to lay on top of the negatives in the holder...