As far as I know, there is no difference other than in opening and saving the design. The RSD file is the collection of all the little files but packaged into one file
When you have the design open, it unpacks the RSD file into the same bits as the individual files. If you are using Windchill (we use it), it does it behind the scenes. If you are opening an RSD file outside of windchill, it unpacks it and creates all the little files in your work directory but does not update them if you save it again as the RSD file.
If you save it as an RSD file and then open it again, the next save will be the unpacked files unless you use SAVE AS and fight with the directories. The open file routine defaults to unpacked files (which remain from working on the design but are not up to date, so you have to remember to change it to packed files when you open it again.
Very awkward to use packed files unless you are using Windchill. They are very useful for sending a design to another person or saving them in a non-working directory as a backup.
If you have Windchill enabled, it automatically saves files in your workspace as packed files but it leaves the initial collection of small files in the non-windchill work area as garbage.
You have to specify to open the file from windchill to work on it but that because automatic. The files in Windchill (or ones that you manually save as packed) do not show up in the recent file list. I have our script erase that list so no one opens the bad copy.
