Depreciation on Motorhomes

We were thinking of downsizing our caravan but are also considering a medium sized two berth motorhome instead. As lifelong caravanners we may switch back so I would be concerned about losing a lot of money over, say, two or three years. Clearly if we bought a new top of the range vehicle for £70 - £75k we could lose a packet so perhaps a two or three year old one would be better. Any views on which make or age (fairly new) would be the most cost effective?