When I started several years ago, the prices were astronomical. The only choice was to buy used and learned to deal with defects. As with most things, they are repairable relatively cheap. Getting a $800 gun for $400 used was a great deal. Now things are different, retail prices have closed the gap. But if you are mechanically handy and short on budget, buying used is definitely better than new.
NEW stuff: unscuffed, you get all the parts that you read about in the reviews. untested (May not work out of the box), excellent wallhangers. need to buy all the accessories which run up the bill (mags, batts, BBs, slings, etc)
OLD stuff: usually 20+% cheaper, tested and usually working (unless otherwise noted in the post), tuned for field play, upgraded, crap stock parts were replaced, usually comes with tons of accessories (slings, mags, grips, scopes, batts, BBs), but usually have major paint wear or scars, may be missing stock parts, loose springs.