Earlier quoted context omitted.
I'd definitely rather have a 5x7 or 8x10 than a 4x5, but film availability for 5x7 seems...limited. I only know of ten film stocks available in a 5x7 format[1] vs. 25 for 4x5[2] (including some C-41 and E-6) and 19 for 8x10[3] (again including C-41 and E-6). And then, of course, 4x5 seems moderately impractical, and 8x10 only more so ;) [1] http://www.ishootfilm.org/film?utf8=✓&film_size%5B%5D=size_5... [2] http://ww…
There is more 5x7 than that - Fuji still make some http://www.japanexposures.com/shop/film-analog/film/sheet-fi... and Kodak Portra is available for special order, and thats just the colour ones. You used to get a bunch in half plate and European metric sizes too, although less now. (I also have an 8x8 back for my camera and cut down 8x10...)
edit: all of the 5x7 film listed there is out of stock :-\