Fleeting Ghost, as an At will move action, I can move up to my speed and make a stealth check to hide, and I take no penalty to stealth check for the movement.
Fleeting Ghost is a level 2 Rogue utility power.
Cunning Sneak is a class skill, I only don't take penalties for moving more than 2 squares, and -5 for running instead of -10. I can make a stealth check to hide if I end my turn more than 3 squares from where I started.
It seems like Fleeting Ghost is a "cheaper" way to get the same effect, except with less stipulations and a reduction from all penalties instead of just a few.
Is there really any reason to get Cunning Sneak over Fleeting Ghost?