Which lighten stains vinegar or lemon juice?

Distilled (white) vinegar can vary in pH. It is usually near 2.5.

Lemon juice is more variable, often ranging between a pH of 2.0 and 3.0 depending on the variety of lemon, the growing condirtions,etc.. So, i guess lemon juice is removes stain better than vinegar since its usually much more acidic than vinegar..