Just picking a current OL team that is almost done...I have 3 lefties:

Cy WIlliams vs L: 226/277/445 (all stats are AVG/OBP/SLG)
Cy Williams vs R: 301/393/625

Lloyd Waner vs L: 320/392/412
Lloyd Waner vs R: 333/375/431

Boggs vs L: 316/392/395
Boggs vs R: 317/408/431

I have 4 righties:
Elston Howard vs L: 338/418/503
Howard vs R: 302/353/429

George Kell vs L: 365/370/496
Kell vs R: 319/369/450

Rennie Stennett vs L: 305/341/412
Stennett vs R: 301/327/369

Xavier Nady vs L: 379/424/552
Nady vs R: 374/409/538

Nady is actually part of a platoon with my AAA OF, and rarely plays against R.

Every player has a better OPS with the platoon advantage than without it.