I bought a 17 on Dec 27th. Could have ordered an 18.
But for me. I had a Ford Customer Cash coupon that expired on Jan 1.
Dealer had a 17 that I was happy with.
18 have a slight price increase, Plus smaller rebates and possible no Customer Cash coupon when the 18 would arrive. And the dealer gave me around $4000 more on my trade than other dealers were quoting me.
Also for me, I'm high mileage. All my trucks are usually over what is considered normal mileage and I get dinged at trade in for having high mileage.
So buying a very late model year 17 will help me not be so high in the mileage. Lots of 2017 trucks that have 20,000-30,000 miles already. I'll still be high mileage in 5 years, But not as bad as if I had bought an early 18.
I don't think there is much difference between a 17 truck built in early November or a 18 truck built in December. I'm just not worried about 1st year vs 2nd model year because a late model 17 was already Job 2. The difference of 10 hp means nothing to me when you already have 440 hp.
All things being equal, Buy the newer model. But there are times when a deal on last years left over can be a better deal.