Think that a better question would be what is the difference between good duct tape and cheap duct tape. The cheap duct tapes are usually thinner and not as sticky. The better tapes have thicker backing, are more durable and have a lot more sticky stuff on them.

Have used the military tape and it is a nice heavy duty duct tape that is not silver. If you are looking to buy a good tape at your local building supply the tapes that are in the $10-$15 range are usually good tapes. My personal favorite is Nashua 357. Have also heard that the gorilla tape (think that it is black not silver) is good also but i have not tried any yet.

If you want to use it temporarily you can also get gaffer tape, it is a little harder to find than duct tape but it does not leave a residue behind. Think that the last time i was at the photo shop they had it for almost $30 a roll. Glad i didn't need any. hth.