The NL Cy Young race is down to two at this point. Jake Arrieta's dominating performance over the last few months has allowed him to catch up to Zack Greinke and in many ways, pass him. Either person is deserving of the award and since I don't really care who wins it, this is just a list of their stats for you to look at it.
You Decide 2015
IP: 223 Arrieta, 214.2 Greinke
K%: 27.0%, 23.6%
BB%: 5.7%, 4.8%
K-BB%: 21.3%, 18.8%
ERA: 1.82, 1.68
FIP: 2.40, 2.76
ERA-: 46, 45
FIP-: 61, 71
AVG: .186, .187
HR/FB: 7.8%, 7.0%
W-L: 21-6, 18-3
WHIP: 0.88, 0.85
GB/FB: 2.41, 1.44
oppTAv: .256, .258
DRA: 2.19, 2.08
WARP: 7.6, 7.3
fWAR: 7.0, 5.7
I bolded the stats that are most important to me if I was to determine this. I'm a biased Cubs fan, but DRA, which is probably the best pitching metric around, slightly favors Greinke over Arrieta. This is such a close race that there is no wrong answer. I am a Cubs fan so I'm going to take Arrieta. I watched almost all of his starts and I'm not sure I've ever seen someone be as dominating as he's been. Pedro Martinez in his prime comes closest and that's some ridiculously high praise as Pedro's prime is probably the best a pitcher has ever pitched.