Well there are different types of stereo linking.
There's the type where just the detection circuitry (algorithm) is ganged (joined) for each channel, so a peak in one or the other triggers both, but the controls are seperate, so each channel reacts differently to the trigger.
Then there's control-ganging, where the detectors are left independent, and just the controls are mirrored (though honestly I can't think of any that work this way)
I suppose you could have both concurrently, too.
The idea of linking the detectors is that you wouldn't want one channel to experience an errant trigger that the other channel doesn't see, resulting in a shift in your stereo image due to one side being sucked down. Though, imo and in my practice, unless you're doing extreme panning/dynamics, the stereo image shift is not detrimental using unlinked detectors.
Generally, I go with unlinked (multi-mono, if you will) because I like what it does to the image. If the soundstage shift bothers me (hasn't yet), I wouldn't use it. Nice thing is, it's usually pretty easy to A/B. Do that.