I looked up some Salesforce documentation, and I am still a little confused on the differences between Email-to-Case and On-Demand Email-to-Case, as well as when should I implement one or the other.
Based on my understanding, Email-to-Case requires downloading an agent behind your company's firewall (and thus is more secure). Email-to-Case limits customization and custom field mapping, but automatically identifies replies, Contacts, Subjects, and other fields. Email-to-Case also accepts emails larger than 25 MB.
On the other hand, On-Demand Email-to-Case just uses APEX, which allows for more customization and custom field mapping, but only accepts emails less than 25 MB. Likewise, On-Demand Email-to-Case solely uses the Salesforce.com platform, so it is less secure (not behind your company's firewall).
Is my understanding correct? In what situations should I consider using one or the other?