I would get the 72" chandelier

I would say 3/4 the length of the table as it will normally be, meaning without extentions if theyre not always inserted.

What is the fixture, over what table? Length is just ONE aspect of many, including ceiling height and specs of the light itself.

Also room style, on a whole. Add pictures and more information.

I think we only have one part of the question . All you will get here is hundreds of pics from beth and you still will not have an answer . Post pics of the space and the table . A pic of the LR so we get some clue as to your style and if you have a fixture you are considering post that. BTW all those are added in a comment here not new posts