Leaving either one on u're face for the entire night isn't a great idea!
topical salicylic acid is a BHA.......excellent exfoliater....which penetrates deep down.....It is recomended by dermotologist as an excellent preventive measure for un-complicated acne....
Benzoyl Peroxide is excellent for un-complicated acne as well and has shown very good results in testing.
I use Paula Begouns Line of skin care.....which includes Salicylic Acid and benzoyl Peroxide.
If you don't know who Paul Begoun is...google her...She has done some of the most extensive research in the cosmetic industry and has shed some light on marketing gimics and provided a wealth of knowledge to the average consumer.
My suggestion is...spot treat your pimple with benzoyl peroxide...start of with a lower dose..2.5 %.....and in between apply a BHA lotion at night. this will really help keep the skin clear.
U also will need a good moisturizer as it could be drying.