I bought a 2015 over the summer, it's the last year of the boxy body shape which I like much better than the newer style. Much more experienced members may chime in but I think 2016 was the first year of the 6 speed tranny which did experience a certain number of issues. If you're going to go for something newer than 2015 it might be better to go with the model years that have the 9 speed AT.
2017-18 EX or EX-L would be my choice - Carplay/ Android Auto, most of the wrinkles have been ironed out, 6spd AT. Might be a bit biased with a '17 EX though Kinda wished we had had the money to go with an EX-L for the acoustic windscreen, but didn't want to pay the extra for all the other things (leather, sun roof) we didn't want. Good luck with your search!
2015 is the last model year of the "old school Honda reliability" in my opinion. The 3rd gens (in my experience and that of others) tend to have more small problems than older Hondas. If you're looking for the reliable Honda experience then get a 2015.
Again, my 2 cents only from a 2016 owner and someone with a last gen Odyssey that had never put a foot wrong. I love my Pilot, but the reliability isn't there like Honda used to be.