Stock answer: It depends on what you want your architectural pix to look like. There is usually no one film that is best for any one application. There are, however, films that are better or worse at meeting named criteria.
My personal answer: For most daytime b/w architecture pix that I would do for my own work, I would probably use Rollei IR400, if the budget allowed. I would even use this film over any slower film, in most situations. It is sharp and contrasty, and due to its extended spectral sensitivity, can be highly tweaked with filters.
So, what are the criteria for your pix to be a success in your eyes, what format are you using, and how large will your prints be? Black and white or color? (I assume b/w, since you mentioned a b/w film.)
Off the top of my head, there are:
b/w:
Kodak Tri-X 400
Kodak Tri-X 320 (discontinued, but still available in retail locations and through various Internet sources)
Kodak T-Max 400
Kodak BW400CN
Ilford HP5
Ilford Delta 400
Ilford XP2 Super
Fuji Neopan 400
Fomapan 400
Rollei IR 400
color negative:
Kodak Portra 400NC and 400VC
Kodak 400UC
Kodak Gold 400
Fuji Pro 400H
Fuji Superia 400
color transparency:
Fuji Provia 400X
Fuji Sensia 400
Kodak Elite chrome 400
