field symbol vs internal variable
Could you explain a little what is the comparison?
Which is more advisable to use?
Field Symbol are like pointer to memory in ABAP.Field symbols points to the assigned data object in memory and doesn't take separate memory. If you change the contents of field symbol, it will actually change the content of memory location, it is pointing to. So you are changing the assigned object.
here are some more links to field symbols
hope it is useful..