Toyota "could" have given us detailed energy information without requiring a NAV. Prius's have a touchscreen and energy info with or without a NAV. Portable NAVs are but a pain in the rear to secure from theft everytime you leave the vehicle unattended. Built-in NAVs are worth it just for the security against theft.
As for updates, even Garmin is producing very few database updates on my spare 4 year old portable. It's been well over a year since the last update and nothing on the horizon.