I've only used Victorinox, so I can't comment on Wenger SAK's.
SAK's are working knives, period. Their INOX steel is super easy to sharpen and gets frighteningly sharp with little effort. The thin blades excel at cutting, especially soft materials. You can safely pry with the (usually) included bottle/can opener. Not to mention open wine, tighten screws, etcetera. Because their cost is a fraction of the New Tactical Knife of the Month, I think some feel as though they are 'disposable' tools. Not so! I love seeing pictures of 20+ and 30+ year old SAK's that have been carried and used everyday by their owner. They've been in space, the frigid Antarctic, everywhere you can think.
Both Leatherman and Victorinox make very robust, dependable multi-tools (Gerber, however, does not). Different animal than the humble SAK.