It depends on what you're looking for. Sometimes it's easier to find what you want used than new, sometimes it's not. I'm backwards - my beater fixie is a Surly crosscheck that I bought new to make a commuter out of; my long distance fixie is a 70's Raleigh Pro that I got used. I'd say I get the most satisfaction out of the Raleigh, because I just really like the way it rides. Various parts have been swapped in and out since I got it; it started as a budget build, but at this point all the components are high end, and I even had it repainted/restored at one point.
If I had to replace the Raleigh, I'd either look for something similar and of a similar vintage, or go get something built custom, because those would be the two options most likely to get me what I wanted. If I had to replace the Surly, I'd probably just go buy another CrossCheck or similar and not bother with the effort of hunting down something equivalent used, even though it probably wouldn't be all that hard to find.