One reason to use slow films is for work with old soft-focus portrait lenses. They often show their distinctive character between f:4 and f:8, and if you use studio strobes, it's not always so easy to get the power down to that level without resorting to ND gels on the lights or ND filters on the lens, which is likely to be very large and some non-standard diameter, requiring some sort of kludge like taping filters behind the lens. It's much easier in that situation to use a slower film.
Other than that, I don't see any image quality justification for shooting an ISO 25 film for contact prints unless you happen to like the general look of that film. I much prefer Tri-X.