I'm working with my teenage artist son as he creates a pen and ink drawing with extremely fine cross-hatching. Nobody would argue charcoal is less an art. So, as a group, we should be able to quickly and effortlessly switch between discussing images which show amazing detail and other images where the amazing qualities are in other aspects such as the ideas and compositions.
My son's pen and ink drawing is going to have the kind of quality I go for when I use 4x5 inch film and enlarge to 11x14 inch print, lots of detail to captivate the eye, and flaws which capture the imagination.
I can see that any contact print is microscopically better than any enlargement. Because I want 11x14 inch prints, I'd shoot an 11x14 inch camera if I felt strongly that this microscopic beauty was the ultimate to be achieved... And yes, I feel it is AN ultimate. But I decided to compromise and I shoot the tiny 4x5 and smaller formats as the mood strikes me, and I enlarge to make my "inferior to contact print" prints. I'm willing to compromise JUST this much. More power to the person who shoots larger and contact prints, I'll appreciate what you've done when I go to see your shows.
In general a 6x9cm negative the size that starts to make breathtaking contact prints. So there would be nothing wrong with a 4x5 inch contact print to my eyes.
Arcturus, You could use 8x10 inch film for portraiture if you want. One good reason is that a large negative can be more easily retouched.