Hi Louise,
I carried out several A/B tests and personal letters perform WAY better. Open rates were up to 200% higher and click rates up to 500% higher when the email was sent on behalf of someone from the staff; option B was sending it on behalf of "CompanyName" Team. On the other hand, the more you use someone's name as label, the lower will be those numbers (it's a proven fact, too) as people seem to get sick of the same guy in their inbox. Maybe at the 20th email they understand it's fake.
But, if you need to get more attendees for some local event for example, and if you're using a small database for this, personal emails can be the best choice.