With the Regular List subscription you will receive an email each time a member posts, which can be many times a day depending on the nature of the topics being discussed and/or the number of events going on at a given time. This is generally the best option if you plan to be a frequent participant in list discussions.
The Digest Version compiles all of the posts for the day into a single daily e-mail message. This is probably your best option if you are signing on to the list only to receive information.
If you're not sure, the listserv program will allow you to sign on to both versions to see which fits your needs better, and you can later unsubscribe from the version you no longer want.