CP
DMVPN provides multipoint any to any connectivity. So if you have multiple end points in your network that need to communicate directly with each other (not necessarily through a hub/central site) then DMVPN is your best choice.
VTI and GRE/IPSec are very similar in their functionality. They both provide very similar functions for a point to point tunnel. VTI is easier to configure and reduces complexity in the configuration since it does not use crypto maps and does not require an access list to specify the traffic to be encrypted.
HTH
Rick
HTH
Rick