I have skied two of those, and they where two of my personal favorites of this years park skis.
Volkl ledge is a little lighter and softer, for someone in the 120 lb weight range it would be perfect.
Chronic is a slightly heavier stiffer ski, still incredibly playful.
Line and Volkl both make kickass skis, but i would bet that the chronic would outlast the ledge. Really your decision all comes down to personal preference, if you like stiffer skis go with the the Chronics. If you are willing to sacrifice a little durability for a lighter swing weight and slightly softer, livelier flex, go with the ledge.
You really cant go wrong, and i heard the THALL kicks ass too.