Quartus II: ALLOW_REGISTER_MERGING & REMOVE_DUPLICATE_REGISTERS

Quartus II has these compiler settings listed below,

the first can be selected from the GUI Compiler Settings, the second from the Advanced Settings.

The both seem to do the same thing, merge duplicate registers, the combined register then will drive the combined logic.

Is there actual a difference between the two? and if not and what happen if they have conflicting settings?

set_global_assignment -name ALLOW_REGISTER_MERGING OFF

set_global_assignment -name REMOVE_DUPLICATE_REGISTERS OFF