Flash memory vs. hard drive

Virtually all of today's cell phones, no matter how powerful, run on flash memory. But this may change soon. Microdrive technology is advancing just as fast as flash memory. The internal difference between the two is that the microdrive is a mini hard drive, while flash is standard ROM digital memory.
The external differences are less clear at this point, but that may change in the future. Right now, both have similar memory capacity -- under 10GB -- and compact size. Flash memory also requires low power and in shock resistant. Hard drives, however, have better data life, faster data transfer times, and will likely soon have more capacity, as the engineering advances. But a a hard drive isn't shock resistant and has more moving parts to break down.
Bottom line: Right now, you don't have much choice. Virtually all cell phones run on flash memory. But this will likely change in the near future, thanks to continuing advances in microdrive technologies.