our()

pros

• creates package variables with ease
• visible across the scope of the file

cons

• clutters package namespace
• visible across the scope of the file
• globals don't scale

my()

pros

• creates lexical variables which are safer and don't dirty a package's namespace
• my()ed variables behave well and will destroy/untie/evaporate when they fall out of scope
• you can do funky things like closures with my()ed variables

cons

• my()ed vars don't stick around long enough to pick up the cheque ;-)

Basically our() is designed for getting around using vars, whereas the use of my() encourages safer programming and goes hand in hand with strict which is a much praised practice in the monastery.
HTH

_________
broquaint