Nail guns are not "all-around" type of tool. Each type of nail requires a specific gun for that nail. Can't use a finish nailer to frame up a house. Can't use a framing nailer to hang sheetrock / wallboard. Actually, there's no nailer I know of that is good for hanging wallboard. Too easy to punch the nail through the wallboard paper backing.
pin nailers (smaller version of a brad nailer)
staplers of all kinds
And each nailer is designed to use 1/2 round nail heads or full round nail heads. Staplers are narrow crown, wide crown, roofing staplers. Some finish nailers are headless design.
So, you must look at the job at hand and pick the nailer for that job. Also, if you aren't going to do a lot of nailing, maybe the hamer would be a better choice.
The deck will need a framing nailer. The overhead wallboard would be better secured by using a screw gun. The screw gun is self loading and drives screws to the correct depth.