Dragon, RX-505 or DR-2 ?

I have the chance to get one of the 3 decks mentioned. 

The Dragon works but the NAAC is slightly out of line, it’s an early serial number which I understand can mean an expensive service. The sales price is of course the highest!
The RX-505 works as expected, just never serviced and is being offered at half the price of the Dragon. 
The DR-2 is near mint and hardly used and is priced between the Dragon and the RX-505. 

Which one one would you choose?
If you dig the cassette holder spins 180 degrees, it´s the RX-505 ; )
Great machine, worked flawlessly for many years, great sound. Have fun !
It comes down to how much you want to spend. You didn't mention any of the prices. The Dragon, sent over to Willy Hermann for service, and you will have the best Nak deck. Of coarse my opinion, and some here will argue that. 
I can only relate my experience. Although I don’t know the DR-2 I have owned the Dragon (that I bought from Willy Herman), and an RX-505 (serviced by Willy). Both machines worked flawlessly, and I still have the RX-505. I couldn’t hear much difference between the two, both were great. If you only plan to listen to commercially recorded tapes, I recommend the convenience of the RX-505. The previous poster is correct that the Dragon will likely be the most expensive one to have serviced. Any higher end Nakamichi is worth the cost of service or repair. You can still find used (and sometimes new) cassettes at thrift stores for almost nothing. If that RX-505 is the lowest priced deck, you may be in luck.
As an owner of a Dragon, I’d choose the Dragon. Regardless of which you choose, all of them will really need a complete rebuild to perform their best. Sure, they may work, but I promise you without a restoration they won’t perform to spec. 
The Dragon and RX-505 have the same transport, which was Nakamichi's best. The DR-2 was a somewhat cheaper design, although still better than most other brands of cassette decks. Sounds like the DR-2 may be priced a little high, but it would be my last choice regardless.
Thanks for the feedback. I’ve secured the RX-505 for $250. 
Congratulations! I would take nrenter’s advice and look into service. It’s worth the money.
Thanks.  Yes I've already reached out to a couple of service places, including Willy Hermann.

Dragon is a definitive machine with unrivaled performances for other decks.
If you do not intend to use it intensively, do not buy it and fold it on one of the other two decks; it would be like having a Ferrari and using it a couple of weekends a month  ihmo
best-groove, Most Ferrari owners use their cars only a few weekends per month, if that often.  Did you see a high mileage used Ferrari?  So, perhaps the analogy is not apt.
mmmm I am of the opinion that things should be used not left to take the muffins. lol
Buying the RX-505 was a good choice, especially at that price. If you decide that cassettes are your thing, you can always move up to a Dragon if you need what it offers. I’m betting you will be happy with your purchase. When I bought my RX-505, the seller had a Dragon for sale but it was almost twice the price and didn’t sound as clear as the RX-505. I believe it was out of alignment. I have never regretted my decision, and the RX-505 is still in my collection.
Each Dragon that i’ve seen before sold for over $1.5k
I love cassettes (good memories of the 90s). I wish to find the Nac deck, but i think $1.5k + service is  too much for a cassettes heaven.
AKAI GX-95 MK II (TOTL) is another excellent choice w/ both level and bias calibration, and is usually cheaper and equals RX-505 in SQ. I have both and I highly recommend them.

AKAI GX-95 MK II (TOTL) is another excellent"

Akai is second rate, budget, low performance option while it is not a bad deck it does not even remotely approach a Nakamichi such as the 505 or Dragon in performance, construction, or audio quality.

Buy a non-functional Dragon that's in good physical condition (that hasn't been adulterated by a tech; ideally a higher SN), and send it in to get a full restoration. There's no point in paying extra for a deck in "perfect working condition" because any deck you procure will need a full restoration to perform at spec.

By following this approach, I became the owner of a 16XXX SN Dragon that is in pristine (and I don't use that word lightly) physical condition and now performs as good as new (care of WHS). Total investment: Around $1,300.
I bitterly regret having sold my CR7 15 years ago, I would not have taken half the money of what is required today to have one because I never thought that in 2019 the Naka were very popular and prices were constantly rising

I had everything, boxes, papers and accessories but I had not used it for a long time and it was practically new; at least I made a happy enthusiast who has traveled more than 1000 km. with the car to come and get her.
I sold my CR-7A probably 15 years ago as well, and my Dragon and ZX-9 too sometime later. I regret selling any of them. The good news is that they’re all still available somewhere on the internet. You just have to accept that you have to dig a little deeper into your savings if you want to buy them back. Just prior to my retirement and a move out of state, my wife insisted that I sell my 2000+ cassettes. Again, I regret selling them but, in retrospect, it was a good decision...but I do miss them!