Julio, I think I should start testing some 400 ASA films, any recommendations from you side?
Alex, I have used HP5+, TMax 400 (TMY) and Tri-X with good results. I guess Delta 400 would be also in that league. In C-41 color my favorite was Fuji 400 consumer film but I do not know if they make it anymore.
Ilford also has XP2 which is a C-41 B&W film ; if you can get C-41 development, XP2 would probably be the most flexible option because that film has incredible latitude and good contrast: being C-41 it is also easier to scan because most scanner corrections and dust elimination tricks are tuned for C-41 films.
As PF said above it helps if you can control contrast with your development.
ISO 400 would be an excellent choice with your Superb or other MF cameras where grain is not so important as in 35mm. I often use ISO 100 (FP4+) in dull weather anyway.
If you can try night pictures with dull weather, you'll be surprised!