I tend not to use 35mm because I find the cameras are harder to use - I wear glasses and the 35mm finders are more difficult to accommodate. About the only areas 35mm still scores over larger formats for me is in macro, long lens work, and remote control, none of which I do very much, if at all.
The 5x4 kit is chosen for the quality of the format, the anticipated need for movements, and possibly no portability issues.
MF gets the general walking around nod, it is a good travel tool. My MF equipment is TLR and rangefinder.
I suppose if I lost everything and had to start over with one camera, it would be a MF rangefinder (6x4.5 or 6x6) or a TLR. I could get a lot done with that. I'm happy to take the constraints of the equipment and work within it.