Try to schedule a single meeting with multiple external attendees - it will take several hours and chains of back and forth emails before you can find a meeting time that works for everyone.
WhoIsBusy is the only tool you need to check the availability of all attendees before scheduling a meeting, making sure the proposed time will work for everyone.
With WhoIsBusy you can create cross-company project teams and invite members to share their availability in real-time with each other.
How it's better: Most calendar scheduling assistants can only show you attendee's schedules in your organization. WhoIsBusy can handle multiple calendars from your external partners, contractors and clients, so everyone can check availability before scheduling a meeting.