An Expansion pack is usually done by the official creators of the game, which actually includes a LOT more to the game, not only 3-4 advantages. Also "Expansion pack" here is useless since people can make Add-Ons.
Therefore:
Your argument is invalid. For me at least.
Expansion packs are also more expensive. Usually from $20-$60.
I doubt RTB's premium features will come close to that.
You're also not forced to pay. You can use RTB without the premium features.
Wait WHAT?! Please do an in-depth explaination.
It's been explained more than once.
IRC is getting removed.
Friends list with group chats is being added.
Benefits of friends list:
-No one can take your name, because it forcefully uses your ingame name.
-You can add people.
-You can see what your friends are doing.
-Better interface.
-Think of it as like, MSN in Blockland or something.
-It's coded to be suited purely for Blockland.
-It's run by RTB, rather than centralchat.net.
Downfalls:
-Please try to find one.