I usually shoot with some cant while on the ground, just because it feels more natural, but as deer season approaches, I switch to vertical for shooting out of a treestand. It is a more forced position, but it has advantages.
I hunt high and get a lot of close shots(under 10 yards). For me, it's easier to get to a true full draw with a vertical bow on those steep downward angles.
It also gives you a near 360 degree arc for shot opportunities because, unlike with a canted bow, you can take shots to the rear without having your bow limbs interfere with the tree or stand.
Practice it all and be prepared for anything.
Canting the bow has never done anything to open up my sight picture. Reguardless of how much you cant the bow, unless you change your anchor, you have to cant your head and equal amount. This keeps your eyes on the same plane with the sight window, regardless of whether you're shooting the bow vertical or horizontal.
For you guys that are seeing more of the field, are you canting the bow and not your head?