Did Federalists oppose the Louisiana Purchase due to practical or political reasons?

The Federalist opposition to the Louisianna Purchase was rooted in a political motivation.  To begin with, Thomas Jefferson, an anti-Federalist, brokered the deal with France.  The political rivalry between the federalists and anti-federalists had escalated since the establishment of the Constitution and neither side could resist the chance to oppose the other.  Another concern of the federalists was that the introduction of new citizens, and potentially, new states would interrupt the balance of power in favor of the anti-federalists.  The further away from Washington a state was, the less likely they were to be in favor of a strong federal government. There was also the likelihood that the states would adopt slavery in the new territory.  These political issues really hit home with the Federalists in the Northeast. 

Why were some Federalists opposed to the Louisiana Purchase?

It is important to realize what a major undertaking the Louisiana Purchase was.  It was far more than what is now the state of Louisiana.  The Louisiana Purchase doubled the size of the new country. A look at the map provided via the second link below shows this.  States were being added to the original 13 states, some territories were moving in that direction, and now this purchase would lead to more states becoming part of the nation.  This diluted the power of those who represented the present states, which they were not pleased about. Furthermore, Jefferson seemed to be exceeding his authority as the president with this purchase.  There is nothing in the United States Constitution that allows a president to purchase land on behalf of the country, and this outraged the Federalists, too.  But Jefferson framed this as a kind of treaty and was able to secure the consent of the Senate, in a vote of 26 to 6.  It is easy to look back and see what a good idea this was, but at the time, it could have been a constitutional crisis.