Interesting... it has roaming. SLL. Free data 500mb.

So other than call rates there is no difference between smart plans and best?

You can check this link here for the Terms & Conditions of the Free Basic Internet:

2. FREE Basic Internet and Free Social (hereinafter to be referred as "Free Internet") Terms and Conditions and Fair Usage Policy

The first few points read:

All FREE Internet promotions including but not limited to the 'Smart FREE Basic Internet' and 'FREE Social/FREE Sozial' are subjected to Digi's FREE Internet Fair Usage Policy fully determined by Digi.

The Subscriber will enjoy the use of FREE Internet subject to the limited speed of up to 64kbps in line with this present promotional offering (subject to change at Digi's discretion).

This FREE Internet is herein restricted from consumption of Voice over Internet Protocol (VoIP) and/or Internet Tethering and/or any Peer-to-Peer or file sharing applications and/or other similar heavy streaming services.

The Subscriber must remain Digi account in Active status in order to use FREE Internet.

The list is a little too long to put here, so you can get it from the link given.