There are not many players who have had the honor to play with both Messi and Cristiano Ronaldo. One of these is surely Carlos Tevez, former teammate of Ronaldo at Manchester United and of Messi's with Barcelona and the Argentina national team. Tevez spoke on his experiences with both players.
On Ronaldo: "He spends the entire day in the gym, it's an obsession. I remember that we needed to train at 9, I arrived at 8 and he was already there. So I tried to arrive at 7:30 and he was already there. One time I did everything to get there before him, I arrived at the pitch at 6:30, but he was already there. He was half asleep but there he was."
On Messi: "Messe isn't like this, to him it all comes naturally. But for what doesn't come natural to him, he trains for. One time he wasn't kicking free kicks well, now he puts them all in the corner. He trained and improved."