"You have seen that with regard to Chelsea before, spending big money," added Benitez.
"The advantage United have is that they have a big squad, in the last years they have spent money to improve that squad even more.
"They have spent big on top-class players, so they can make mistakes and they can change players. When we won there, they had Ryan Giggs, Paul Scholes and Dimitar Berbatov on the bench.
"We cannot do something like that. We spend too much time worrying about whether Steven Gerrard and Fernando Torres can play while they can play Cristiano Ronaldo, Carlos Tevez, Berbatov or Wayne Rooney - it doesn't matter to them."
Benitez led Liverpool to victory in the Champions League in 2005 at the end of his first season in charge and then guided the Reds to FA Cup success in 2006.
They had a reputation as a team more suited to knockout competitions but the Spaniard believes this season's title challenge has changed that tag.
For the last two weeks of the season, teams fighting for the title or to avoid relegation should have their matches all at the same time
Reds boss Rafael Benitez
"We have done well. Clearly we are more consistent," he said.
"Once we were a team for the cups and the Champions League and now we can talk about being a team for the Premier League. That is positive for the future.
"We will now continue to do our job this season, and next season it will be different."
United will play Arsenal on Saturday when a point will be enough to wrap up the title before the Reds play at West Brom on Sunday in the penultimate round of Premier League games.
"This is a strange situation," said Benitez. "Having games so close to the end of the season on different days. It is something that should be improved in the future.
"For the last two weeks of the season, teams fighting for the title or to avoid relegation should have their matches all at the same time.
"The last two games should be the same for everyone, in Spain it is like this."
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