I am one who has often not recommended buying regionale tickets in advance, because there is no price advantage and because they can only be bought one week ahead.
But, I can think of a few advantages, as well:
- You can bypass the ticket window line or the kiosk (sometimes avoiding a line, or "helpers") and go directly to the train
- All your tickets can be placed together, as hard copies or in an e-format, no need to remember to buy a regionale ticket
- Tickets do not need to be validated, so no need to remember to stamp some tickets (regionale) but not others (trains with reserved seats)
EDIT: Buying online in advance, not in person. Thanks, Bob!