This depends on the size and variability of your volunteer numbers. Here's what to keep in mind:
Annual contract: With the Annual Plan, you commit to paying for one year of service, while there is no contract with a Flexible Plan.
Price: With the Annual Plan, you pay less than with the Flexible Plan. See pricing.
Removing users: With the Annual Plan, you commit to paying a once-off fee for a that covers you for a full year. You can't change this until it's time to renew the contact. With the Flexible Plan, you can upgrade or downgrade at any time and your next monthly payment will go up or down accordingly.
The Flexible Plan might therefore be best if you have a variable volunteer force. For example, organisation that provide once-off services might double in size during the summer months. A Flexible Plan allows these organisations to provide temporary volunteers with Complyfile and only pay for the service while it's used. Volunteers can then be deleted when they leave at the end of the summer (if that's ok under your policy and procedures).
The Annual Plan might be best if you have a larger group of volunteers and your team is generally growing in size. On the Annual Plan you effectively pay a lower per month rate (as we give you a month's free usage).