I would do drywall unless you have a garage like mine. It is detached from the house and does get some water in during heavy rains. I opted for 7/16" MDX. I don't have to worry about finding studs when I hang certain items which makes it nice. Think of a garage drywall job as good practice. It's a garage. If you really want it to look nice hang it yourself and then have someone else come in and mud/tape. That won't be "cheap" however.