Capsules are absorbed for much longer than powder. Apart from that, their top absorption occurs in the guts. Their great advantage is an accurately measured dose of creatine closed in a capsule casing. It is also worth noting that the casing is neutral for the organism. Metabolically speaking, the difference between capsules and powder is so negligible that it should have no influence on the supplementation choice. The only criteria worth considering are the price and comfort of use.