9 Things you can do on Google+ which you can't on Facebook or Twitter

This is not an exhaustive list, it's a few of the things I use commonly which can't be done on Facebook or Twitter (or elsewhere).

1: Can I make a public post?

• Google+ Yes.
• Facebook No.  Public posts on Facebook are not visible to logged out users. Related post.
• Twitter Yes.

2: Can I mention someone in a public post?

• Google+ Yes.  Though whether that person is notified of the mention of them will depend upon the settings they have chosen.
• Facebook No.
• Twitter Yes.

3: Can I define streams of posts from different groups of people?

• Google+ Yes.  Circle streams feature public posts and posts the users have shared specifically with you. 
• Facebook No.  You can make lists which can include "public posts" (Facebook's definition) from those who have turned on the following option. You can't include people generally.
• Twitter Yes. 

4: Can I post privately to an individual?

• Google+ Yes.  Though as before you cannot force notifications to an individual or page. 
• Facebook No.
• Twitter No.

5: Can I "finish" a conversation I have started?

• Google+ Yes.  You can turn comments, on your posts, off when you are done.
• Facebook No.
• Twitter No.

6: Can I turn native sharing of a post off?

• Google+ Yes. 
• Facebook No.
• Twitter No.

7: Can I categorize my posts by topic?

• Google+ Yes.  You can use Collections for that. 
• Facebook No. 
• Twitter No.

8: Can I add someone else to a private conversation of mine?

• Google+ Yes.  If you have a private post you can bring someone into that conversation with a mention. 
• Facebook No.
• Twitter No.

9: Can others add someone else to a private conversation of mine?

• Google+ Yes.  If you allow them to: i.e. if you have not locked the post. 
• Facebook No.
• Twitter No.

Reply to me or comment using Google+ below.

Comment or reply to me using Facebook. 

Comment or reply to me using Twitter.