Ten years ago, a NZ rental motorhome was usually a manual Fiat Ducato 2.3 with five gears and a sluggish first-to-second shift on hill starts. Today the Ducato comes with a 9-speed automatic that handles every mountain pass without intervention, and most major fleets have converted their newer vehicles. Manual gearboxes are still around — mostly in older Hiace-based campervans and budget-tier 2-berths — but the rental rate difference is small and the comfort difference on a 14-day NZ trip is meaningful.
Why the automatic is the default recommendation
Most NZ rental driving is on State Highway 1, 6 and 8 — long, undulating two-lane highways where the automatic stays in the right gear without input. Mountain passes (Crown Range, Haast, Lewis, Arthur's) are where the difference shows: the automatic downshifts on the climb without you thinking about it, and engine-brakes on the descent automatically. With a manual, you're working the gearstick every few minutes for hours.
When a manual is OK
If you drive a manual at home daily, a budget-tier manual 2-berth on a shorter (7-10 day) trip is fine. The fuel economy difference is negligible on modern vehicles. The rental cost saving over an equivalent automatic is usually NZ$10-25 per day — meaningful over a long trip but small over a week.
What to ask the depot
Confirm "automatic transmission" on the rental agreement before signing. "Auto" can sometimes mean automated-manual (AMT) on older vehicles — a clutch-less manual that shifts itself but still has the lurch of a manual on hill starts. Torque-converter automatics (the more common modern option) are smoother.