My favorite medium speed B&W film (ISO 100) is Fuji Acros. In terms of grain and resolution it is at least as good as the two main competitors, Delta 100 and T-Max 100, but what sets it apart from these films is its very low reciprocity failure. Delta 100 and T-Max 100 are a lot better than traditional films, but Acros is in a league by itself in my experience. In low light conditions you will often find that because of the low reciprocity failure of Acros actual exposures time will be less than with ISO 400 films.
I use Across with Pyrocat-HD, 1+1+100 at 72F for 15 minutes and get great resolution and virtually no grain at 20X. However, Acros is a robust and easy to use film that should also give great results with a wide range of both staining and non-staining developers. In my opinion Acros is easily the best medium speed film on the market if you consider ease of use, grain, resolution/sharpness, and low reciprocity failure.