The linkage just gives the shock a better progressive rate... Hence the stock rear shock is a single rate spring. As long as the shock is setup properly for the setup you choose.. they both work fine. IMO the progressive rate that the link provides doesn't affect the drag bikes much. Most of the bikes with the long swingarms only use 12-12.5" shocks.. which only have about 4-6" of travel.
So my vote goes to a no-link setup unless your swingarm is already a link style. (I've used both in the dunes) Like J-madd said, Its not worth spending the extra money to go to a no-link if you arleady have a swinger and shock setup for a link.