What gauge nailer should I buy: 15, 16, or 18?

The consensus across carpentry communities is that 18-gauge brads are best for delicate trim, shoe molding, and cabinet assembly because they leave tiny holes. 16-gauge straight finish nailers are the most versatile workhorse for baseboards and casing, and 15-gauge angled finish nailers are preferred for thick door casings and crown where extra holding power matters.