Which method is more used an why?
There seems to be two schools of thought regarding implementing Custom Data on Macs
create a plist and place into /Library/Application Support/LANDesk/data
create a XML and place into /Library/Application Support/LANDesk/CustomData/
My environment is currently LDMS 9.5 sp3 moving to 9.6 shortly
This really depends more on preference. Both are viable options and should give you the information you need.
Retrieving data ...