I know the prowler does nt need a waste tank so some space saved there, but unless you relying on a garden hose tap you will need a clean waater tank. They take up fair bit of room.
Also consider times you take a rotary or even your true portable (Prowler heavy), plus all your hoses, wand, vac cleaner, tubs of this and that, sprayer(s) etc.
Sprinter ok but Vito not so good apparantly.