Both of them are less of a "boot" and more of a "wake from hibernation" sort of thing, but most of the issues are the same -- you still have to boot a kernel, whether or not you're gonna populate the system with a saved state when it's ready.
ENGADGET: Lineo's Warp 2 boots to Fedora on Atom in 4 seconds, MPC Data's SwiftBoot warms up embedded Linux in an instant