There are a lot of subtle differences between the characters that not only add to the asymmetry of the picture, but also say a little bit about the characters and their differences. Like I mentioned, that was one of the funnest parts to do. For example, you can see that Superman is actually much taller than Batman, but if you include his ears then Batman is taller. Batman and Batgirl are both standing with their legs apart, like they're in a stance to fight. But Superman and Supergirl are just standing with their legs together because they don't need to be in a stance. It's little things like that.
Practice makes improvement when it comes to drawing the same character over and over (or anything really, but especially this). Though this is the first time I've drawn two of these characters from the side, I think it looks awesome. The hands are probably the weakest part of the picture. I still haven't mastered drawing hands (obviously). I wasn't sure about having the mouths on the sides of the faces instead of connected to the front, but I think it was the right choice for me at least.
God blessed this drawing so much I can hardly process it. It could have been such a mess without His help. Thank you God.