On a general level I thought super-fine grain and stain do not really coexist since most super-fine grain developers use sulfite to produce the fine grain effect. I guess an exception could be a developer that relied on the developing agent itself for solvent action (eg ppd?) instead of sulfite, meaning you could use ppd in addition to a second developing agent like Pyro or Catechol and get stain with fine grain. But does Pyro have to be the primary developing agent to produce imagewise stain?
If you are just starting, it will make little difference which you choose.
Xtol or D76 would be my suggestion because there are so many people familiar them, they are very flexible, and very capable of producing very high quality work. Either could be used for the rest of your life very easily.
You need to look at a whole host of developers from Johnsons, they were around at the birth of photography until poor management in the 1960's and their withdrawal from chemistry in the 1970's.
Also some Ilford Patent developers, Sease, Edwal and Chamlin, and then Kodak HC110 used to use pyrocatechin.
Pyro is grainier than Xtol and is delivers a bit less speed. I've tried pyro and catechol developers from time to time, and I like the look of the prints with medium and large format negatives. They seem to give better highlights while retaining reasonable shadows. But most of my B&W work now is with 35mm, where grain is a factor.
I have lots of 35mm Tri-X negatives, processed in Pyrocat-HD, and they are very sharp indeed. Grain is about on par with Rodinal, which means it's relatively fine grain, but what appeals to me is the visual impact of the contrast that the stain yields. Super sharp and high acutance. Beautiful stuff to work with.
I also remember it working exceedingly well with Ilford FP4+, which I used in both medium format and 35mm, and those negatives print like a dream to 12x16 or 16x20.
Pyro based developers harden the gelatin of the film during the very first stages of reduction, grain is set at that point with relatively little change to the grain's accutance or appearance no matter the length of exposure to chemistry.
Whereas, developers with a significant presence of Sodium Sulfite do in fact promote silver migration during the last stages of exposure to chemistry. Such migration and lack of stability directly go to the accutance and impression of sharpness in the final negative / print.
MSDS information on Xtol shows a moderate amount of Sodium Sulfite makes up the formula for Xtol.
Lastly, I have never looked through a microscope at any negative, I have however seen tests done on Tri X & FP 4 developed with HC 110 and the Pyrocat HD. THese tests were conducted by a respected moderator on the LF Forum and bare out with striking clarity the thoughts I shared above.
I've gone back to ABC rather than Pyrocat for negatives I want to develop in a staining developer because of this higher accutance. But only for large format contact prints.