IMO the roms should load a bit faster as well, since the drive won't have to do "random" read/writes between front-end, emulator, and rom. Less back and forth seek time is always a good thing.
That being said, you'll see almost the same performance if you defrag your hard drive, then ghost (capture and image and write it back). Ghosting will also help a bit in the defrag department, but it's also nice to have a backup image of your drive, as well. Doing the defrag/ghost will make almost the same difference as a solid state drive will, in performance, since you'll be negating your drive seek time, and that's not a bad thing at all.