The two major form autosave implementations I can think of are either based on cookies, or based on periodic ajax updates to the server.
I'm trying to decide which is a better option.
The advantage of cookies is that it's not server intensive, and with some good code can be implemented to not pollute the user's cookies. The server update implementation is probably portable across user sessions (depending on how it's implemented) and even user logins across machines. However, in my case user portability isn't key and incremental data isn't too useful so I don't really care about this advantage.
What are the other major pros/cons of either approaches?
Thanks!