Nice picture of Angels Landing, Laura. They call the squiggly switchbacks "Wally's Wiggles". They used an earth-tone concrete to pave that section.
Here's my rating: I have done all three, and I don't usually get intimidated by heights.
I'd rate Angels Landing the least intimidating. There were entire families up there! The exposed part is fairly level trail. As Laura says, if you step away from the chains and off the trail, that would be dangerous. I don't think I even used the chains.
Half Dome cables is next. There, if you let go, you're going to hurtle down the granite. So you MUST hang on! But the cable is there, and it is strong. Except when it is so cold that your hands freeze and you can't grip, or wet and slippery, you're ok.
The Final 400 on Whitney: It is all up to you. Still not THAT bad from exposure, but you must pick your own hand and footholds. There is no obvious route, so you have to look around and decide where is best to go. Takes more care and watchfulness, in my thinking.
