Multi-lam is stronger.
Stronger is better.
No?
Stronger is better, but multi-lam doesn't make a neck stronger or stiffer. Depending on the grain runout, a multi-lam can be weaker, but with straight grained wood (what we hope they use on our necks, it usually works out to be about the same as one piece of wood.
A multi lam does, if you use the wood grain right, reduce the likelihood of it twisting or warping. Wood comes out of the tree with stresses that, over time, will relieve themselves. With a laminate, you can (if you choose or cut the wood properly) make the various parts of the neck tend to warp against each other, so the net result is a straight neck. Another way of keeping a neck straight is to anneal it via Roasting - done properly, that process relieves the stresses in the wood, so that when you cut the neck from it (you anneal the blank, then cut the neck), the neck is stable.
A place where adding another piece or two of wood does help with strength is in an angled back headstock - a scarf joint joining an angled piece of wood (so there isn't grain runout behind the nut) can make that kind of neck stronger than a neck made from a single piece of wood, because the grain is running the right direction where it counts.
+1
Multi piece necks also help if not totally eliminate dead spots.
Again, using two pieces of the same species of wood, and gluing them together, doesn't change the stiffness of the result, so no, it doesn't help with dead spots. If you use a LOT of laminations, and a LOT of glue, you might introduce enough damping to help out a bit, but the way most necks are made, you're not going to materially change the vibration pattern via laminating a few pieces. Graphite rods can help some - they are stiffer than wood, so adding them to a neck will change the way it behaves, often (but not necessarily always) for the better.