Foma 400 is lovely in Rodinal 1/50 for 12 minutes, 35mm is a bit grainy but nice grain, not a problem for 120,a lovely combo, IMO better than kentmere, which is fairly ordinary, as far as problems with Foma, in 10 years+ of using foma all the time I have yet to have any QC problems, [roblems yes but all down to my own mistakes
I used lots of Foma 100 in Rodinal without problems. I generally shoot at EI80 and pull the development to 8minutes in 1+50 to make it a little more flat. I get a very nice tonality in the negatives and it prints (and scans...) quite well.
Price - varies
Pre hardening Foma is softer I only use plain water stop and temper but squeegee
Contrast build Foma builds contrast more quickly.
Speed Kentmere is at box speed Foma at data sheet speed