I'd say power centralised at the Federal Government because that's what power tends to do -- it tends to centralise.
Those who have more power tend to find ways to use that power to (always with the very best of intentions) to obtain more power. Whenever the Federal and State governments argue about who has a certain power it always winds up looking like a wolf and a chicken arguing about what's for dinner.
Power does not always centralize. For instance the long-term trend in Canada has been towards decentralization. According to the Constitution there are many things that the federal government has sole responsibility for that in practice have been moved to the provincial level (with the blessing of the federal government).
Those who have more power tend to find ways to use that power to (always with the very best of intentions) to obtain more power. Whenever the Federal and State governments argue about who has a certain power it always winds up looking like a wolf and a chicken arguing about what's for dinner.