[iainmd]

If you tow or regularly carry heavy loads consider HD, otherwise stick with standard.

If our rears ever need replacement I'll be going HD as on a family holiday with 4 of us, a full roofbox, 4 bikes on the towbar mounted rack and a full boot the car's backside is nearly dragging on the deck. For he time being I fitted Grayston spring assisters.

As I say though, if you only ever carry a light to medium load then standard springs will do you fine.