Over the last 2 seasons, Porcello has been worth 7.1 fWAR and Cole worth only 5.6.
Considering that Porcello skipped most of the minors and did a lot of his development work in the majors, he's been a remarkably consistent pitcher over his career. His 2016 does stand out, but so does Cole's 2017 as a career year. And for as young as Cole is, Porcello is only 21 months older, which isn't much considering he has 4 more full seasons of MLB experience...