Better to have single butt joint or 2 tapered joints when hanging drywall?
There are merits to both. For structural support (yes, drywall adds some shear support) you want fewer joints and drywall crossing as many studs as possible. This has the side benefit of reducing the amount of taping needed and may use less mud.

For visual appeal, tapered joints are easier to completely hide with mud. Rather than spreading out the mud over a wide area to minimize the visibility of the joint, you can completely fill the taper for a perfectly smooth transition.