Like, Deepvalley, I shoot left-handed, and I've never owned a left-handed gun. With semi-auto pistols, rifles, and shotguns, by the time the recoil and noise have died down, the spent casing is long-gone, and I don't even notice them anymore. I wouldn't worry much about where the shells are ejected. I've never been hit or distracted by shells ejected to the right. The same is true with pumps.
More important--as deepvalley said--is that the stock isn't cast off for right-handed shooters, and I also prefer a tang safety, which is ambidextrous.