2 in 1 shampoo and conditioner or both of them seperatly.. which one is the best of hair?

I don't think this: is a medical question; I don't think there is any actual medical science on this. In general, you don't need conditioner on your scalp unless it is very dry, so a separate conditioner can be more easily applied to the mid-to-ends of the hair shaft. Don't pick based on price, fragrance or foaming. Try various products until you find one that makes your hair look great and feel good:)