I've been a bit of a butterfly in the past, having used pretty much every film and developer on the market at one time or another. Now, however, I've decided to get tough.So……
VP/PMK- The finest combo for MF around, IMHO. V fine grain for a 50 yr. old film and tonality that was good enough to eat -the kind you just don't see with modern films. Fantastic for portraits (did some great wedding shots on it). Pity VP is now no more, but such is life (better get some more APX 100 in 5x4 while I still can).
Forte 200/PMK- Great combo for LF. Tonality that's smoother than a cashmere codpiece as Stephen Fry would say and great price too-just over £35 for 25 8x10s.
APX 400/PMK- The old AP400 was the very first film I tried with Pyro-I was instantly hooked. Becoming my mainstay for 6x6, especially for portraits.
Delta 3200/Rayco UFG- Lovely rich negs with good shadow detail and prints to match. FX10-see the Darkroom/Film Developing Cookbook is a very similar formula. Lengthy dev time (16-18 mins 24c at 3200) but as a Guinness ad put it, good things come to those who wait. Love it for portraits.
Polaroid Type 55- No dilemmas about which developer to use with this film! Another favourite for portraits. Obviously much quicker to process and no more fiddling around reloading darkslides or carrying them around (well not till I get my 8x10 anyway).
There is no Holy Grail (" no thanks, you see I already 'ave one"...) in films or developers (PMK comes close though) so work on that vision thing and don't get obsessed with chasing the BEST combo. 3 or 4 films and devs should just about cover any situation you might encounter-probably you'll use a couple of these most of the time. That said, a little bit of experimenting goes a long way-that's how I discovered my current faves (hmmm...must try Delta 3200 in 777 some time).