They use a combination according to their preferences. Some use Twitter more than IHUB, others may use email more than they use either Twitter or IHUB. It depends on what they're most comfortable with. But there are few who don't use at least two of them.
One thing you'll need to keep in mind re: email is that not all emails will arrive to their destinations at the same time. For whatever reasons, some may get delayed. With Twitter, this is not the case. All of a person's followers will receive the tweet at the same time.
If you decide you do indeed want to use Twitter, click on my IHUB user name at the top of this post and you will be directed to my profile. Scroll down a little and you will see "Follow me on Twitter." Click that and you will come to a page on which you will need to request to follow me. Once I approve you, I will follow you and will also send out tweets to my followers about your new board.
Good luck and I'll be looking for you on Twitter. :-)
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