CanadianDriver.com had a very large comparison of drive systems and snow/all-weather tires. Their conclusion is "it's the tires." They also observed the AWD systems of Mercedes and Toyota Highlander to be their favorite. The AXD Ford Five Hundred was a surprizingly good performer.
Components such as ESC and ABS were much more important than coupling systems. To illustrate how our Canadian neighbors value snow tires over AWD systems, look at their review of the BMW325ix. The reviewer would take a 325i with snows over the added weight and complexity of the AWD 325ix.