INV automatically scans your server for un-guilded patrons and invites them to your own guild if you have the appropriate permissions to do so. It allows for level customization, random informational messages that you supply, and function toggling so you can either message, invite, or both.
Most importantly however, INV will remember everyone that it invites on a per character basis, and will not automatically invite them in the future. This means that any given character will receive one invite at most from your person. Since mass recruiting is a pain, automation helps a lot. INV does this without the annoyance of repeated invites to people who don't want to join.