I have to agree that the Mac 250 Entour is a better fixture then the DS250. More gobos, more colors, 16-bit control over a few more things (the 16-bit of rotating gobos I find very useful when using custom gobos with logos/words on them). Cost wise, it runs around 3 grand on the net new however. At that point, you can either get nearly 2 DS250s. Or you can add about $200-300 and get a DS300 which has one feature you don't see in a Mac spot until you get to the 700 Profile roughly 7 grand latter, CMY.
Buying used moving lights is like buying a used car, not 100% sure what you have until a few months or few thousand miles down the road. Moving heads I prefer to buy new, things like LEDs however I don't mind buying used. No moving parts, LED life rated for years.