ofcourse GSM has better encryption. as compared to

TETRA - Terrestrial Trunked Radio

An open digital trunked radio standard defined by ETSI (European Telecommunications Standards Institute).It is currently being used by the emergency services to replace existing PMR (Private Mobile Radio) systems.

and

DECT - Digital Enhanced Cordless Technology

Digital Enhanced Cordless Technology uses the 20MHz of spectrum between 1880MHz and 1900MHz, DECT provides 120 duplex channels to provide wireless speech bearers. Enhancements to this standard now allow data services up to a data rate of 1Mbps to be supported.