When planning a VPN deployment, for which reason does an engineer opt for an active/active...

An active/active FlexVPN configuration allows for multiple routers or VRFs to act as hubs for different VPN groups, providing load balancing and redundancy1. This is useful when the VPN deployment has a large number of spokes or different security policies for different groups of spokes. DMVPN, on the other hand, only supports a single hub or a pair of hubs in active/standby mode for each VPN group2. This limits the scalability and flexibility of DMVPN deployments. Therefore, an engineer would opt for an active/active FlexVPN configuration as opposed to DMVPN when multiple routers or VRFs are required. References :=

Cisco FlexVPN: Benefits and Best Practices

Cisco DMVPN Design Guide