Both have options.
Monasterio had the better spring and is the more traditional utility infielder, but he is behind IKF on the deoth charts.
Eaton was with the Sox last year, played in the WBC, fills the need for an OF off the bench, and is one of the fastest runners in MLB which gives him usefulness as a pinch runner.
To me, no brainer. Keep Eaton and demote Monasterio.
I suppose the Sox could keep Thaiss over either of them while also keeping the versatile Wong in the team, but I think that’s a long shot…