I agree with the kids on the longer end.
If you are on a 173 for slalom, you charge and have control of those things.. I raced on a 150... but im also almost 100lbs lighter than you.... Anyway...
I'd say min of 180 and if you go rocker, maybe even a tad longer. Shorter and you will end up disappointed when you start picking up speed and they noodle out. Also, if you race, go for something stiffer. Im sure your legs are a lot stronger than what a lot of the park skis like and you will be fine pressing pretty much anything. Also, cause it's what youre used to, going to a soft ski would probably take away from your learning curve if youre already trying stuff out on the race skis.
Kudos on the switch! Best decision I ever made.