Two preamps are available....

Question:  Two preamps are available for sale on Audiogon.....both are listed at the same, identical price. 

One is factory refurbished and "as new" with manufacturer's warranty from an Audiogon dealer and the other is in 9/10 condition from a private seller.  Both sellers have excellent feedback. 

- Which one would you buy and why?  
- What are your positives and negatives about units that are factory refurbished?

I'd go with the manufacture date as well.  If the "refurb" unit was a dealer demo, having working in some high end dealers in the past, most of the equipment on our floor had LOTS of hours on them, most turned "on" in the morning, left "on" all day, six days a week.  Back in the day I bought a "demo" NAD receiver which developed a left channel out problem, and the "warranty" the dealer gave me was worthless, they never fixed that problem.
Thanks, ejr1953.  I will ask.  The refurb unit will come with a 3-year warranty which is "good news" in my humble opinion. Just hope it's not a dealer demo as you describe above. 
Sorry, but I'm going to jump in here again.  I was in the high-end audio business for over 25 years.  Not once did I ever send a "demo" unit back to the manufacturer, (unless there was an upgrade to the model).  We always sold our demo units at a discount.

I would be more worried, (if I was to worry over such a thing) that the used unit might have been a dealer demo.

Also, as good as NAD is, it's not a McIntosh.

Again, buy the refurb and don't worry, be happy :-)
+1 for @mofimadness 

McIntosh doesn't fool around.  You'll own it until it becomes an heirloom or you get bored with it.  It doesn't get higher value than that.