I am not enamored with any particular format although photographs made with my Koni Omega (6x7) sell well ;-)
I too use all formats from 35mm to 4x5. However my assessment of the type I would recommend always comes down to the Hasselblad (6x6). It seems to have every advantage: light weight, interchangeable lenses, interchangeable backs (choice of films), choice of either between-the-lens or focal-plane shutter, no parallax problems, essentially bullit-proof, and ----
Holy cow! I already have a camera with these features, a 4x5 Speed Graphic. It does seem to be a little large and heavy in comparison.
Truly, dr bob.