I would shoot one bow if could maintain good form throughout all my shots for the number of shots I like to shot in a day, and do it with a bow weight I like to use for hunting.
If I only shot light then jumped up in weight for hunting I would have better form training, but I don't think I would have as good of strength and control to apply it unless I made the change mid summer.
If I was really training with good form with the heavy bow and shooting comfortably I would see no logic or need to go light to hunt.
For me only shooting a heavy bow can lead to sloppy form because I like to shoot a lot; my release gets sloppy, and I don't get full extension after a while. I think most target shooters shoot lighter bows than the bows they use for hunting so they can maintain good form to the end of a long shoot, and for extended quality practice.
I usually have two bows about 5# or more apart. I often shoot both most days when it is not hunting season. Some days or weeks I only shot one. I like to shoot light to work on fine tuning form, shooting endurance, and just so I can shoot a lot. I shoot heavy to apply the form I have learned and to build strength. I get them to both shoot to about the same place just by using lighter arrows in the lighter bow. When the end of summer rolls around I shoot the heavy bow with less shots per day and more varied shots. I only shoot the hunting bow during hunting season, and I only hunt with one bow.
If I only hunted and didn't want to shoot a lot everyday, I would probably only shoot my hunting bow and keep my shot count within what I can handle without form breakdown. I just can't shoot 100 or more arrows a day and not develop bad form with a heavy bow. I also find it much easier to condition and work up in weight by shooting light and heavy bows as part of standard practice.