Choice of Vandersteen models

Assume the price for either will be the same. Quatro Wood(not the CT), or the 5 (not the 5a or CT). Both in excellent condition. Don't discuss alternative speakers, other than these two. Which will sound better, which will hold value better. I have Modwright OPPO 105, and  NAD 375BEE amp, 150 Watts Per 2 channel. 
You may want to check the Audio Connection website. I think they had at least one of the speakers you're considering used. Having had the 5A's in a room that was 23' X 12', my guess is your room size should be a factor in your decision. 
I'm pretty sure the Quatro Wood will have the "tri-woven" midrange driver. If the model 5 pre-dates that driver, the decision should be much easier for you! Then again, the model 5 can be upgraded to 5 Carbon.
Also consider whether you will able to take advantage of the Vandersteen upgrade program; the 5s can be upgraded all the way to 5A Carbons.  I'm not sure if there is an upgrade program for the Quatro.  Worth checking with a Vandersteen dealer.
I think the upgrade program is for original owners, but going through someone like John Rutan at Audioconnection might grease the wheels...
As for your original question,
It depends upon how large your room is. I own the Treo’s (non CT), and they work perfectly in my 20x18 room-even in non traditional positioning.
I would expect the Quatro’s to work as well in the same space.
The 5’s might overwhelm a room that size. Once again, Johnny would be the best person to give advice on that subject.
As far as ’holding value’ goes, once a newer model comes out the older one drops. In my opinion, I think the Quatro to be the best in terms or resale ability, and the easiest to work with in a wide range of rooms.
I would go with Quattro's if your just comparing them to a Model 5. But you should seriously get yourself a 5A if buying new or from a local retailer. You may be able to get a demo pair for a decent price.
The first version of the wood Quatro has a lower midrange suckout. Kind of like some older DM B&Ws but worse. 
the 5a is no longer in production, so we are talking used
they are about tge same money 5a and Q-Wood used
the mid suckout was floor bounce and was solved in collaboration with the reviewer who noted it ( and gave a glowing review ) later models have a tweak to make the room interaction less critical, but you could call factory.
As for value used later...they are pretty much tied today, easy form factor and WAF with the Q, better ( much ) lower bass in the 5a assuming you are in a room that allows for that..
as to uogrades, available to origional purchasers only, and priced that way.
long time 5a and now 7 owner with a pair of Treo coming...
speak to John Rutan at Audioconnection. 5s need HUGE room college auditorium size. 
Midrange suckout? Are you referring to Stereophile's measurements? That "problem" is because Atkinson has to measure at 50" in his "quasi-anechoic" technique, and he doesn't always use the manufacturer specified height. This severely handicaps first-order designs in particular. Compare, for example, Stereophile and Soundstage's measurements of the Thiel CS2.4. Stereophile shows a big "suckout" in the upper midrange/lower treble while Soundstage shows near ruler flat response from ~35-20K cycles. Why the difference? Soundstage has a real anechoic chamber and, more importantly, measures at 2 m = 79".

I disagree that the 5’s need a HUGE room. I have a fairly small room and use 5’s and they sound quite good.  A bigger room would be better, but it’s not a necessity.  Having said that, the Quatro Wood may be a better choice for a small room.  I got my 5’s here for $5k several years ago, at the time Quatro Woods were fairly new so very few used for sale and when they came up they were in the $7k range.  The bigger issue is finding a used pair, don’t see them too often so if you are picky about which wood species you want then you may have to have a lot of patience.  Good luck!
agree 5 do not need a massive room
in fact tge 11 bands of bass EQ allow them to work just about anywhere....
RV has an anechoic chamber also , poster just taking a shot he has made before.....facts and engineering seem to get in the the way.....

to the OP
some quick calls to the some Vandersteen dealers might be in order as many do a lively trade business and may even have access to customer units when they trade up
i would try four in particular but there are more:
Johnny R at Audio Connection in NJ
Alan Jones at Hi-Fi Buys in Atlanta
Bruce at Stereo Unlimited in San Diego
Randy at Optimal Enchantment in Santa Monica

Randy has I believe a pair of 5a used in maple or oak right now
i bought a pair in Rosewood from him used some 7 years ago now....
Alan took them in trade for my 7
good luck
pm me if i can help in any way
My brother took me to Casa Guadalahara, if only I knew Stereo Unlimited was a few blocks away...
I heard them before the stereophile review. I have heard a later version and the ct as well. First hand, I consider it a notable issue relating to the op question. I don’t google measurements to post them here.
The Quattro Wood is a newer and (probably) more refined speaker, but the 5 offers greater placement flexibility with the rear-firing tweeter and the different subwoofer configuration. Personally, I’d go with the Quatro, but I don’t think you can go wrong with either option.  
Thank you all for your input. I have notified Bruce and Randy to call me if.... Both being local(ish), I can avoid shipping costs. Please keep me in mind if either pops up in your universe.
And, if you are like me, and want to save some cash, you can buy a pair of Treo's and 2wq subs and get 90% of a Quatro.
When I got the Treo's, I didn't realize that they share a similar footprint. But, now I realize that the Quatro is a bit deeper(due to the included sub) and it works better for me and my room- The subs can be moved to inconspicuous areas and still do their job.
I do know that John at Audioconnection has a pair of Quatro Wood's used, for sale. See the website.
FWIW, I had a pair of 5s and now a Quatro Wood (non-ct).  The
Quartos sound better than I could ever get the 5s to sound.  But I'm sure this is also influenced by room and upstream components.
I have two sets of loudspeakers, Vandy 5A and Von Schweikert Unifield Mk3.  Both pretty great.  The Vandy's are my preference of these 2, mainly for the bottom end.  You will be happy with either of your choices, I am confidant.  I would take the 5.  
The Music Room here has a pair of 5, not perfect but a decent cabinet guy could fix the dings and you could get Vandersteen to recover the hoods.
Rob is the guy I deal with there - straight shooter
they are a large dealer here on the gon and I have never been disappointed in the 5 or 6 deals I have done with them...