Torsen is a design that in theory works well as it distributes power to the axle shaft that has the greatest resistance, it has not a proven record of reliablity. The design that has done well over a period of time is the ARB air locker, which is an open differential or when air pressure is applied is a spool. The OX locker is very similar other then it uses a cable to engage total lockup. The Detriot locker has proven to be strong and it will lockup, the downside is it is not on demand and will lock whenever you apply pressure either through throttle opening or deceleration, it only is an open when you have no "load" against the driveshaft. There are many variants to the lockers lited above. The most widely used differentials other then open are limited slip, clutch type OEM units.