What are advantages and disadvantages of unicast and broadcast in xbee s2c?

What are advantages and disadvantages of unicast and broadcast in xbee s2c?
In general, most articles recommend to use unicast.
Please explain that.

I find that the article located at http://knowledge.digi.com/articles/Knowledge_Base_Article/XBee-ZigBee-Addressing/?q=addressing&l=en_US&fs=Search&pn=1 explains it well.

Also you need to wait about 3 to 4 seconds between each broadcast transmission to allow it to Travers the network before you can issue the next Broadcast.