Is it better to create many smaller Commonwealths or a big one?

3) I do not use Commonwealth and I dislike the idea.

3.  Why would I give away production,  research,  etc for no return? 

This might make me a dictator but I try to avoid creating commonwealths for as long as possible. One rule, one armada, one purpose.

The only commonwealth I ever created was just to get the Steam achievement for doing so.  I agree with Moser_Alchemist above - why would I give away the production?

Seems like the consensus is to not use Commonwealths altogether. 

Blah, Blah... boring, unimaginative players above.  :) 

If you you don't use commonwealths then you're missing a part of the game. It's not giving up production, it's being politically savvy. That is, if you choose to play in various styles of the game and choose to stay consistent within that style, you will get to a point where your # of colonies will be more than your current government can handle. As a result, many players just decide to choose whatever gov't type meets their needs to win the game.

Which is much different than playing and saying, "I'm a monarchy and my family and it's heirs will never relinquish power unless conquered or overthrown." Therefore, if I want to continue to expand my empire but don't have the requisite advanced gov't within the monarchy theme, I'll need to create commonwealths. Same holds true if you're trying to play as a values based democracy all the through to the end. 

Another way to look at commonwealths too (and how I decided to first try to use them after thinking like the above players' posts), is that if you already have large number of planets to maintain, and a few more won't really make a difference, it's a bit like putting your colonies on auto gov.. Plus, they are loyal followers too, and will support you in a war. Therefore, in my opinion, it just makes the game have a little more political depth and interest. 

I am the president of this Galactic Federation, and I'm smart enough to figure out how to keep my people happy despite the morale penalty.

We are synthetics. We have no need for such meatbag concepts as commonwealths. The Quantum Singularity shall prosper.

It would be best to have multiple Common wealths because each one pays a tribute to you.

Commonwealth's crash on creation the moment I try to customize their icons, portraits, or such. So I don't use them.

Instead ... As sovereign ... I just order planets I can't support be rendered uninhabitable.

I don't know about the crash, but if it doesn't commonwealths are a great way to make money. Commonwealths need at least three planets to survive. I would make sure there is at least a shipyard too. Also customize them. You should gift them a nice fleet of ships just to make sure they don't get the diplomacy penalty. If you like money then more the merrier. If you can;t sustain them then you will gain more citizens for planets. Nice to see you in galactic civilizations. I would recommend not trying your all farms stradegy except for an end game tactic. You do need factories here. I also know from galactic civilizations 2 you don't colonise more than 15 planets, so commonwealths would probably be welcome here. Maybe we can play a multiplayer some time. I've been reading your posts for a long time now. I used to use my name Michael Whittaker. Glad to see here now. I feel like I've known you for awhile because of galactic civilizations 2 posts. I used to post there to in 2012-13.