I personally don't think networks help too much. You can make money off your videos without a network.
But should join a network if:
1. You need to get paid in paypal (google doesn't pay via paypal) If you don't have a bank account you might have to join a network so you can get paid.
2. You really want good royalty free music and don't know where to go. Networks provide a library of royalty free music for you to use. If you weren't in a network you might have to pay for the music or find music somewhere on the web.
3. You want a better dashboard. Networks give their users a dashboard that is usually more in depth then the normal dashboard. However, for really small channels, I don't know if that matters.
4. You trouble with YouTube a lot, whether it be copyright, or not knowing how to upload or anything in-between. If you are having a lot of problems, you might to join a network. Networks have dedicated support teams that can help you if you need it.
5. You have potential of things off YouTube. This is exclusively for bigger channels but you prove yourself, networks can get you a manager, tv appearances, brand deals, and more.
You have to be okay with giving a % of your money of any of the features above.
Should you join a network? Take this simple two question test to find out:
1. Is there anything in list 1-5 that I really want/need?
If no, don't join a network
If yes, move to question 2
2. Would you be willing to give up 10-40% of your money in exchange for the feature(s) above?
If no, don't join a network
If yes, join a network
If maybe, do some research on networks think about it some more.