It is actually quite hard to decide. I guess you could say barrier methods could be considered more reliable, due to the fact that they physically stop conception (for example, a condom physically stops any sperm from reaching the egg) compared to hormonal methods, which rely on hormones to trigger certain responses in the body that prevent pregnancy, but hormonal methods, such as the oral contraceptive pill, have been reported to have a high success rate. However, hormonal methods have been known to have different side effects due to the sudden change in hormones in the body, and may not be as effective on each person due to every person's hormone balance to be different. Also, certain barrier methods (eg. condoms) help to prevent the spread of STIs/STDs, which hormonal methods do not do.