I'd leave it whole. For more bark, trim off the fat cap and any other external fat. That will give more nice surface area for bark. There is plenty of internal fat on a butt to keep it moist.
Cutting a large hunk of meat in half doesn't reduce the cooking time that much.
Rescued 22.5" OTS. SJS Mini-WSM. HEB briqs (rebranded Royal Oak). Pecan/Hickory/Cherry/Apple/Peach woods.
2016 Fuji Absolute 2.0 LE (for burning off all the great BBQ)