Chris Davis or Cespedes?

So I highly doubt I'll be able to grind enough for Rizzo. My current outfield consists of Flashback Ichiro and... he's really the only notable one, the others being silvers and 1-2 golds (Fowler and Pollock, nothing special). My best 1st baseman right now is the 86 rated Flashback Billy Butler, plus a couple more 84-85 rated. Sooo, idk who's more worth it, Davis or Cespedes? Also, who do you think is more likely to get a rating increase as the season goes on? Thanks.

EDIT: Or should I just wait till the next diamond reward comes out?