In January 2013 i bought the Craftsman version (21833) brand new in box for under $350 using a variety of discounts at a Sears. Actually, bought it online while sitting in the store parking lot to save something like $75 compared to buying it "in-store". The Ridgid version is 13 amp, c-man 15 amp. The c-man included dado insert, extra cost at Ridgid. Beyond that virtually identical. Good saw, better with the Kreg miter gauge (i have an Incra 1000 HD i've put into service yet--no complaints on the Kreg). Factory fence is okay, but finnicky with the set screw adjustment to keep it square--so I also added an Incra TS-LS fence which is much nicer.
I'd not hesitate to purchase either of those if not abused, but...Used at all, without getting some extras--i'd not be a buyer at over $250 and that would take being in pretty doggone nice shape. If i were selling mine today, with the Kreg miter gauge and Incra--i'd not expect to get more than $550 if that.
Just my opinion.