Biggest differance is GETVPN is without tunnel and DMVPn is with tunnel, You can save you IP pool.

GET VPN

Simplifies branch-to-branch instantaneous communications - Ensures low latency and jitter by enabling full-time, direct communications between sites, without requiring transport through a central hub

Maximizes security - Provides encryption for MPLS networks while maintaining network intelligence such as full-mesh connectivity, natural routing path, and quality of service (QoS)

Complies with governmental regulation and privacy laws - Helps you meet security compliance and internal regulation by encrypting all WAN traffic

Offers management flexibility - Eliminates complex peer-to-peer key management with group encryption keys

DMVPN

Lowers capital and operational expenses - Reduces costs in integrating voice, video with VPN security

Simplifies branch communications - Enables direct branch-to-branch connectivity for business applications like voice

Reduces deployment complexity - Offers a zero-touch configuration, dramatically reducing the deployment complexity in VPNs

Improves business resiliency - Prevents disruption of business-critical applications and services by incorporating routing with standards-based IPsec technology