Digital BW, The Print

I'm heading out to Utah this weekend and to the Sierra's next month. 
I understand that film scans may likely result in better data files
for printing.  I have a Canon 20D; Nikon 35 mm film and a medium
format film camera.  My question is, should I shoot the 35 mm and get
high resolution scans or shoot with the median format?  After
scanning, will the medium format platform out-perform the data I can
get from the 35 mm sufficient to offset the additional effort?  My
second question pertains to choice of film.  Should I shoot with
Velvia, Tri-X or maybe just color film and convert to B & W in
Photoshop?  Finally, does anyone have a recommendation for a reliable
film-scanning service?

Thanks to all.  I appreciate your thoughts.

Tom