My preferrence is for square format first and formost, followed by 4x5. I rarely pick up a 35mm these days. My twelve year old daughter loves 35mm, and 4x5, lately she has been eye-balling my Mamiya C-220 and asking many questions about using it,I caught her burning a roll of CHS-25 I had loaded in my C-330(portraits of mom and sis). I guess what I'm saying here is to shoot what you love most, and not be too overly concerned with the rest(unless you have a specific project planned for one format).