The beauty of a true double wishbone suspension is the axle path can be tailored by adjusting the length and angle of the wishbones to do anything you want and by altering the way the shock is mounted controls spring rates. for example you can have it set up to dive in the early part of the travel but not at the end, you can have rising rate spring rate, You can have short trail throughout the travel, and most importantly as Vinney says stiction thus small bump sensitivity is reduced. etc etc.
Disadvantges are complexity and high loadings on the balljoints, indirect steering path
