In MXA's test of the 2012 ktm 250 sx they highlight the difference between the linkage and non linkage from 2011. Basically once both systems are set up for the rider/track they are on par with each other. It is just that most of the time the linkage system can be suited to the rider in a matter of clicks where as the non linkage would sometimes need a spring change, as swapper said, the linkage works better over a wider range of conditions where non linkage is more fussy to spring rates etc