If its the gas models you're looking at, Serena for me. Its the newest platform amongst the 3 and when you remove the rearmost side facing seats, you'll get a 7-8 seater van with good legroom and ample baggage space as compared to the Starex/Space Gear 7 seaters.

Hows the overall reliability and parts availability of the CRDi engines vs the older 4d56? I've seen some going for repairs at BBC and they didnt look that good.