If Pearce hits RHP better than Moreland, this is a recent development and probably a marginal difference. For his career, Pearce has a .743 OPS vs RHP, which is less than Moreland’s .780.
Pearce did have a .828 OPS vs RHP last year, but only in 130 plate appearances. Moreland hit his career .780 vs RHP last season.
I’d be hesitant to expect too much from Pearce. He’s a good bench bat/weak side platoon player, but the Sox are probably better off not expanding that role too much...