I need help with newschooler language!

What's the difference between "sick" and "ill?" As in, "dude, that line was sick" or "my new skis are ill."

Is ill the sickest a thing can be or is sick the illest?

And what do you tell the doctor when you are feeling genuinely ill? Imagine the conversation between the newschool doctor and patient:
"Dude, I feel so not ill."
"I know dude, you look so not sick"

It was much simpler when things were rad, cool or even groovy.

Maybe I just need to chill, or take a pill. Or go skiing.

So nice that it's nasty, So bangin' it's bustin', so ill that it's sick, so dope it's disgusting.

From an oldschooler:

IF slang is designed to be mysterious to those who don't know...

"Sick" fufilled that need nicely, but was doomed by it's ultimate popularity.

It was adopted by guys like me so it became "lame."

Maybe Ill is just Sick 2.0.

I can't wait until other words get flipped for slang.

"Dude, how was your run?"

"Man, it Sucked!!!"

Words are nothing without context. It is not about a hierarchy of radness. It is more about the flow and musicality of the phrase. Ill and sick are interchangeable in denotation, IMO, though I think sick is easier to use in a phrase.