I looked at both. If there are differences it would be an internal sort of part that Toyota updated in their continuing quality program.
I think the answer can be situational: my wife wanted the '17 (pure emotional newness factor) and I wanted the '16 ($$). She won.
Now if you trade in every two years, then depreciation based on model year might make up the $$ Difference. Around me I have seen a couple of sales for new '16 and '17 model years that were only about $2K apart.
For what it's worth the fleet manager at my local dealer says the specs for the '18 model are unchanged, but admitted there could be interior/exterior cosmetics as that doesn't get sent out to the dealers until later in the year.