When is 6max a necessity?

I was doing my usual multitabling of the 100nl fulls tonight and noticed the crazy action over at the short handed games. I know everyone says 6max games are more profitable, but I still haven't made the switch because I'm too comfortable with my current games. Anyway, at what limit is 6max an absolute necessary switch from the full ring rock tables?

[2PAUL2]

from experience they get pretty nitty at the 200s but i dont think i would ever wanna put myself through the pain of 400nl full. to be honest id think about moving now cos 100nl 6max on party has got to be one of the juciest games around.

paul