Personally I think you are comparing apples and pears, let me explain. One of the saws (6365) is an older model (looking at the picture). The 6390 is more modern and the advantage of this saw is that you can reposition the handle so as to cut from the top standing over the saw. Or cutting on a table where you can adjust the handle so that you can push it in an easier fashion. I hope you understand my explanation.
If not please PM me I will try to find pictures that demonstrate what I am trying to describe.