so both are chemical exfoliants, but AHA tend to target the surface of your skin, as well as providing moisturizer; whereas BHA targets both the surface and the pores. Therefore, BHA could have effects on acnes, sebums, oil glands... in general besides exfoliation, while AHA main target is just exfoliation. However, BHA tend to dry down your skin, while AHA are able to provide hydration and moisture to your skin. if your skin are on the drier types, AHA would be a better choice, if you're oilier, or suffering with acnes, sebum, blackheads... you might wanna try BHA. if you're dry skin but want to target acnes or blackheads, you could use BHA but be sure to moisture your skin well (before and) after the treatment. if you're oiler but don't need to target on acnes or pores... AHA also works for you, but be sure to flexible the moist or hydration level of your routine, cuz i've heard for some people AHA provide more hydration that they need and lead to increase oil secretion - which you might want to take into concern.