What are the difference between HSRP, VRRP and GLBP. and Which Protocol is preferred over others and why?

Hot Standby Router Protocol (HSRP)

Provides default gateway redundancy using one active and one standby router; Cisco proprietary.

Virtual Router Redundancy Protocol (VRRP) An open-standard alternative to Cisco's HSRP, providing the same functionality.

  Gateway Load Balancing Protocol (GLBP) Supports arbitrary load balancing in addition to redundancy across gateways; Cisco proprietary.

VRRP doesn't support IPv6. HSRP and GLBP do support IPv6. GLBP supports Load Balancing, other2 doesn't. So it depends where you want to implement and what features you are looking for.