My problem with the multi-tool as a main survival tool is strength and durability. I've broken three in the past two years. Two Gerbers and a Buck Whitaker. Both of the Gerber's broke at the locking mechanism while using the knife blades to cut tough rubber material with heavy downward pressure. The lock bar actually broke completely off on both of them.
The Buck started to seperate at the hinge on the folding blade, until the blade was very wobbly. It won't tighten up.
I'm convinced that part of this is due to inferior steel that's made in China and Gerber production isses in China. I have a Gerber Military Tool (not a well known model) multi tool from the early 90's that's made in the USA and it's TOUGH. The knife blade takes an edge and holds it. The downfall on that particular one is that the handles are uncomfortable as heck, the knife blade doesn't lock, and the screwdriver bits are very short.
I've been disappointed with the Gerber multi-tools for some time now. They just aren't as good as they used to be. I know many people who have broken them. And it's not just one model. I've seen broken examples of each one.
I've gone back to the original-- Leatherman. I've had several of these and they have all performed WAY above any expectation I've had. I've never broken one and I've never seen a broken one. I currently carry the Skeletool with the 420HC main blade. I don't like 420HC steel, but that's the only one that was in-stock at the store that day. Since I normally carry another folding knife, sometimes two, it's not a big deal. I love it because it's got a pocket clip and doesn't have to be worn in a belt sheath.
I always carry a fixed blade knife whenever I'm outdoors, along with the Leatherman and couple of folders in pocket or pack. If I had to pick just one, it'd be a fixed blade knife. No worries about breaking or failing at the wrong time.