"A lefty who has a .450 ROPS/900 LOPS or a righty who has a .450 ROPS/900 LOPS?"

If its a starter, I take the lefty. Most of the time a lefty faces 7 righties and 2 lefties, giving you an overall OPS of .550, while a righty would face 4 righties and 5 lefties, giving you .700 OPS.

A reliever is a little different since you have more control over who they face. Tough call in this case. It would depend on what the rest of my bullpen looked like.