There are millions of people all around the world who are members of various whatsapp groups and facebook groups and many people are using these groups to promote their services/products. Which one is more helpful and beneficial for marketing/advertising purpose?
My choice will be Facebook groups. As facebook groups has not only friends but so much more. They have co-workers, like minded people, people who like about what you offer in the groups, people who appreciates the knowledge which you give in the group etc.
Fb groups a clear choice for me too. Whatsapp groups are only a small amount of people who wants to talk and share within the group and not to others.