StingList.AddString adds the whole string to the StringList.Collection while StringList.Add adds each word as a separate item when a literal value is used.
sl←StringList.New''
sl.AddString'first 100'
sl.AddString 'PROPTYPE eq "A"'
Old way
sl←StringList.New''
sl.Add CharString.New 'first 100'
sl.Add CharString.New 'PROPTYPE eq "A"'
Using a multi-word literal on StringList.Add results in multiple items being added to the collection.
sl←StringList.New''
sl.Add 'This is a sentence.'
would have resulted in
'This' 'is' 'a' 'sentence.'
instead of
'This is a sentence.'