The invisible hand which guides pricing will tell about resale value. I was always told not to base a purchase on the item's resale value. Go with your gut on this one.
I, personally, was suspect of Deere's wisdom with the -03 series. After climbing on one recently, I'm even more suspect. For instance the little steel pawl attached to the fender which is supposed to keep the gear lever in Park wasn't close to doing its job. And speaking of fenders, what do you call those crude, flat things shielding the rear wheels? I felt that there was too much cost-cutting on this tractor
Are you looking at a loader as well? Take note that the 510 cannot be removed from the tractor without hours time.
Personally, I'd seek a nice, used 5300, 5310 or 5320 if you require something green. I feel that the color of the paint and the price is what sells these things.