I'm pretty much the same size (+ 5 lbs or so), pretty much the same level, maybe a little below: I ski mid-west blues and blacks, carve at least some of the time (says the instructor, not just me), working on turn shape and speed control on steep(er) stuff. On groomers, 'cause that's all we've got.
I have these skis and really like them. I have the 174, bought the shorter one partly to make turning easier (see above about speed control on steeps...). For turning, side-slips, moving from carve to slipping around a turn, skiing anything from hardpack to 5 inches or so of fresh, they're great. With one qualification: there seems to be a speed limit, beyond which I lose a little stability. It's about as fast as I care to go anyway, and probably faster than I should go.
If your son likes speed, is comfortable turning on steeps, in crud and in tight corners, maybe plans to take them into deeper snow, I'd say get the 181s. At least as of a few weeks ago, there were some pretty good deals on 2011-12 models to be had.
Disclaimer: NOT an expert. NOT somebody who has tried a whole bunch of skis, though I do have some basis for comparison.