Superman is generally considered stronger. He has greater experience and his powers seem to have reached a higher level of potency. However, it can vary depending on the specific comic storyline and interpretation.
It's a great read. The art in 'supergirl new 52 graphic novel' is really stunning. The colors are vivid and the character designs are detailed. Supergirl is portrayed in a new and interesting way, which gives her more depth compared to some previous versions.
The 'Red Daughter of Krypton' storyline is quite popular. In this, Supergirl has to face a clone of herself created by Lex Luthor. It's a complex story that delves into Supergirl's identity and her place in the world. She has to battle her clone while also dealing with the moral implications of being a Kryptonian on Earth.
Well, you might find suits like the one with a golden trim for special powers, or a darker, more edgy look for when she's facing intense challenges. The range is wide and it all depends on the creative direction of the comic book writers and artists at the time.