I agree with the previous posters concerning large format vs medium format. I've used 4x5. I loved it. But I'm older, lazier and fatter than I was at that time. My back and neck are also a mess these days--probably caused in part from carrying heavy photo equipment daily for so many years. Then there is the issue of enlarging and the need for a large format enlarger. They are not cheap and they take up a lot of room. There are lots of good reasons to use large format cameras but there's also good reasons to choose other options.
Actually, I would love to have an 8x10. I've seen some of Weston's contact prints and they are inspiring.