[Freeswitch-users] Difference between last_bridge_to and signal_bond

Hello, Looking at this for the purpose of putting a and b leg CDRs together: http://wiki.freeswitch.org/wiki/CDR#Putting_Together_CDRs I noticed that ${last_bridge_to} and ${signal_bond) are always the same in my use scenario. Is there any real difference between the two and if so which on is better to use? Thank you, -Victor