You can see the daily rewards for each day by hovering over the single days. There is of course a difference between the rewards for free and Premium account characters. Apart from that there are certain rewards where characters can choose from a list of items. These lists depend on your character's vocation, level as well as the game world type.
Also, there have been adjustments in the past, so the rewards now differ from earlier rewards.
If you have any further questions, don't hesitate to contact me once more.
Tibia Customer Support
I submitted a help ticket as per my curiosity when doing a test of what daily rewards I would get. I realized the list would change when testing it on other characters. Cipsoft sadly wasn't able to give me a list of differences but only confirm my suspicion. However, interesting I could never find a news article or anything talking about this. The only way you would know there was a difference is if you paid attention to the list of rewards (the potions and rune list on the 1st, 2nd, and 4th day) and if you had characters in other worlds or various levels.