Tow Pro: Suspensions on caravans

Hi I am looking to buy a traveller platinim caravan. Thay have 3 types of suspension The straight axles with leaf springs 2 The simplicity independent suspension and the Cole over with shockers. My queston is witch of there would be the best to travel on dirt roads for long periods and not shake the caravan to bits with in the frist year ?

Tom, SA