what would you do to get a better composite than this?

For a start off, why did you change the background aspect ratio?  It looks dreadful squashed like that.

You tried to match the background to the two young ladies, which was a mistake because the contents of the background contains clues to how it should look, like the street lights.  The brain is good at recognising things like that without knowing why.  It just knows it looks wrong.  So you need to adjust the lighting for the two ladies.  I am going to try doing this with Camera RAW

First thing to do is make the composited ladies layer a Smart Object so you can edit it until it looks right.

The girls used Camera RAW to increase exposure, and contrast, and add quite a lot of Clarity.  I also took out some of the red and reduced vibrance because they were too red.

I also used some sharpening to get them closer to the background.

The usual rules of perspective say that eyelines should be on the horizon/vanishing point, but you can take some liberty because the camera is held low and pointed up.  Even so, the girls are a bit big for the scene.  I reduced their size a bit,but didn't want them to be lost against the background, so we'll call that a bit of a liberty, and ignore true perspective. 

Note what I said about using Smart Objects.  I went back in and changed the Camera RAW settings several times before I was happy.  Best practice is to leave something like and come back to it with fresh eyes.  You invariably see mistakes or stuff that could be better.

They needed some rim lighting from the lights behind and above them, so I ctrl clicked their layer top load it as a selection, and stroked the selection using Centre on a layer clipped to the girls.  I was then able to blur the stroke and ctrol where it fell with a layer mask.

I said that you crushed the background, but you can still compress it a bit using Edit > Content Aware Scale.  This selectively brings elements closer together without squashing those image elements.

Adjust the lighting on both - they seem underexposed.