Kiermaier will give the Rays exponentially more defensive value than Loney will–that is not up for debate. However, Loney is a more formidable hitter, making this quite possibly the Rays’ best offensive lineup versus left-handed pitching.
It will be up to the Rays to manage the tradeoff between offense and defense, but it is clear that this is a lineup that makes sense in certain situations. One example could be if the Rays see a favorable offensive matchup for Loney that could tip the scales between him and Kiermaier.
In addition, this lineup is nice because Brandon Guyer finally gets to play the outfield. There would certainly be times where he pushes Souza to DH in Lineups A and B, but given that he is a better defensive player in left than Forsythe is at any position, it is a little bit strange that the Rays’ optimal defensive lineup doesn’t feature him playing the field more. I guess we can call that “The Kiermaier Effect.”