
don't get too worked up about it! I don't know much about Kim Tae Hee, actually I know nothing about her. I've only heard of her so I really can't comment about her.
But as far just JJH goes, she's basically an ICON. Especially after her laser printer CF and MSG. You may already know she was known as the CF queen due to all her CF's. Companies choose her as their spokes model because she can sell their products. There was an increase in sales once Olympus signed her as their spokesperson.
She's like a chameleon when it comes to her looks. She can be innocent, girl like next door one moment and be sexy the next, and sometimes she mixes it up and is both at the same time! Looks/fashion wise, she's never slutty and is always classy.
JJH is very selective with her movies/projects. She does one movie per year, if that even.
I also read in one of the sites dedicated to her that she is also the biggest shareholder of her managing company sidusHQ and was giving something like 5 million won worth of shares. I just can't remember which site I read it on.
Those are just somethings about her. But honestly if your friend prefers KTH, I really don't now if you'll be able to change his mind! If should be enough for you to know that JJH is better in every single way!