I still find HP5+ to be my favourite and most versatile film. It seems to agree with everything I throw at it, from Pyro, Rodinal, Johnsons Super Fine Grain (1950's recipe) to H110; each producing pleasantly different results depending upon what I've wanted. I've had some stunning results shooting at 3200 (compared even to Delta 3200, the HP5 had less problematic grain imo). It also doesn't seem to scratch or damage easily, the opposite to what I experienced with foma films (their Retropan and 400 films have no scratch resistance when wet from the wash) . It does help that its a native film for me (UK- Cheshire), so I can get it for far cheaper than the alternatives.
As for grain, the staining developers (pyro or metol based formula) work really well for cubic grained films. You don't get the same grain (I would say far less) as with modern developers and it produces really nice prints. I don't scan, so I couldn't tell you what effect the staining would have for scanning. The stain does change the colour of the neg into ranges which affect VC papers, which is something I like (although it can get in the way for certain types of print). This effect can be used to produce extremely fine grained and high quality prints which are hard to produce with just a filter alone, but this does require some trial and error (and can be extremely frustrating). I did try a Johnsons metol developer with a delta film once and it didn't work out, although it may of just been a one off mistake. As for different developer types and different grains, I have noticed some differences, but I don't know any magic formula or method that would make HP5+ less grainy than Delta 400 (or TMax etc) with the same development routine. The biggest help for low grain in film is being diligent and putting the work in, although I have never had problems with my films being grainy except if I'm doing a stupidly overambitious enlargement (like using only 3mm of a 35mm neg for my print) or if I've underexposed badly. That said, there is only so much which can be done about grain and there are some films which are inherently more grainy than others, although (other than deliberately grainy films like Retropan) modern films all have extremely fine grain and great characteristics. Its amazing how little you get, especially if you compare how much grain you get from plates and what old films above ISO 80 used to produce. A 35 neg will be far less grainy and better for enlargement on a modern fast film than my grandfathers 1930's and WW2 ISO 25 4 x 5 negs ever where. Even comparing prints and negs from the 1970's and 80's to what's being produced now shows an amazing leap in quality and standards for film and paper.
