I'm a cheapskate and buy almost of my cars and hobby stuff used (basses, amps, hi-fi gear, trombones), in part because it allows me to buy better quality stuff for less. It also permits favorable resale if the item is not a keeper. And with instruments, I find that axes that have been played (but not abused) just plain sound better...happy to take an axe that's already broken in! On any high-end bass line, buying used makes sense because you don't know whether you'll truly dig something until you've had a chance to use it for a while, and ideally you won't get burned on the flip. Plus, you can survey used items to find out what wood/neck/electronics/body package works best for you.
That said, once you find something you like, you can dig in and invest in a new item that completely floats your boat.
I'm in the process of doing this with Sadowsky. Several years ago I briefly had a late '90's P/J, but couldn't get used to the 5-string. Now I play 5 almost all the time, and a used R5-24 Metro has been my number one for the past year. I've now just taken delivery on a used 5 string NYC jj, which is allowing me to check out an ash body and single-coils. I'm quite likely to order a new Sadowsky sometime this year, probably a Will Lee 5, but I first want to sort out which of my current axes is better for me; the R5-24 can't quite give me true old-school punch and thump and sometimes doesn't work so well in my playing with acoustic musicians, but it sings like crazy and I'm addicted to the bridge-pickup burp. I wish I lived near Chasarms and could check out his R5-24 with a mahogany body...
As for Metro/NYC, from around 2004 on the NYC axes have improved neck construction and chambered bodies, so the Metros are a bit heavier and theoretically less evolved on the neck. I don't know... for sheer playability and musical satisfaction, my Metro R5-24 has hung with any other Sadowsky, Alleva Coppolo or other high-end axe I've ever been around and features, hands-down, the very best 34" B-string I've ever played, even better than the NYC Sadowskys I've been around.
So my hierarchy: on construction, NYC Product from 2004 on is arguably superior, but no reason to believe earlier Sadowskys would be notably better (other than based on exotic woods or the benefits of age) than a good Metro. Some say the really early NYC Sadowskys have killer necks - I can't comment.
One thing for sure; some Sadowskys are better than others, but they all were built to play, and to last, by people who have their ears on straight. This is one serious company, and I'm thrilled to have access to their work.