The innovation in Apple’s “Safe Sleep” is that it goes ahead and writes out the disk image, but then suspends to RAM. If you just resume, everything’s already in RAM and you can avoid the delay from resuming the image. If you lose power (or change battery), then it resumes from the disk image. By comparison, Windows offers both suspend-to-RAM and suspend-to-disk, but not at the same time.

You can change the Mac’s hibernate behavior using pmset; here’s the reference for it: