Full PPR Flex Help

I’m in a full PPR league and can’t decice who to start

My RBs I have Leveon Bell, Kareem Hunt, and Jay Ajayi
My WRs I have Larry Fitzgerald, Demarius Thomas, and Stefon Diggs.

I can’t decide between Jay Ajayi and Stefon Diggs for my flex spot, who should I start?

I’m in the exact same situation and I’m starting ajayi he was my 2nd pick in the draft and I’m anxious to see what can do. Since he is suppose such a big part of their offense and I think I would start Diggs and Thomas