Hi, dolphinpod (great answer, Bama BTW) also agree on David's key point.
The 2013 will probably hold its market value pretty well for awhile if you wanted to go that route, using it for 2-3 years, retaining the extra camping goodies, and with that adventure time, possibly learn exactly what you might want on a newer unit, which would put you close to the 2020 models by then. (Not that you couldn't have adapted your '13 to perfection, at that point.)
With the 2013, the lift kit is a nice plus, and moving to 15" tires after a year, by just buying a factory set mounted on 15" rims for the axle from FR would get you set up well for the years following, while lowering the # of revolutions of those wheel bearings.
Downside, if you want to use a bank and spread your outlay out into a RV loan, (keeping more funds liquid) the interest rate may be not as choice for the '13, and the loan length shorter than on a '17.
Upside of the new one, is maybe you could negotiate the R-dome into the deal, and use your 2013 option to get the salesman to budge on a sweeter deal. Tires would already be 15's, probably not the lift kit, but like Bama says, a lot of the needed camping bits that go on the hitch, inside, and in the storage hatches could rack up quickly past $1500+ .....so you could tally how much of that would come complimentary with the '13 deal.
With new, you do get at least a one year solid FR guarantee that everything stays working exactly as it should, but you need more than a few trips that first year to make that guarantee possibly pay off.
Good luck with your pro-con list. I would say that if you haven't given the 13 (+ free accessories) an extreme close look, try not to feel pressured at the show to buy the '17 that day. As you know, salesman love that "what can I do to get you to sign today on the unit?" 'show special' statement.
But, if he's a good man, his deal won't fall apart in the following weeks, allowing you to decide to take your time, and choose your '17 later, back at the dealership yard.
I think we're all behind you whatever you decide. Main thing is to plan to get out and explore America and rack up some good Pod times in this era of less expensive fuel. (And may that last!)
Brad & Layli
179 HRE (WanderPod)
BG (10 Tundra)
Western NC