Bit of a newbie here , What is the difference between the two . Im presuming its the compound on the pad or that one lasts longer ?.

Might depend on the type of riding, I guess. But for "normal" trail and XC riding disks are more than adequately powerful, so sintered is the obvious choice. Much more durable, and easily powerful enough. Even sintered can wear surprisingly fast in the wet and grit, organic are much worse.