Diffs

I was doing a bit of digging around the internet looking for info on the gearbox in my car. Found a site that had a PDF with info on all Subaru gearboxes. Looking at the Legacy's some (mine) came with an Open diff and others a Helical diff with an LSD option.

I tried googling the differences but nothing that was understandable. Can anyone explain the differences, and which would be the best to have in your car??

Helical has to do with how the gears are cut. Helical are cut at and angle. where as straight cut gears are cut straight.

I presumed all diffs were helical cut?

Similar to how PPG gearboxes are built.