Hamilton heads to the south of France at the top of his game after a run of four successive victories.
Despite such domination, Hamilton only has a three-point cushion to Rosberg after a mechanical failure in Australia brought his season-opening race to a premature end.
It means every point is precious and every shred of detail vital if the 29-year-old Briton is to win his second world championship.
Asked whether this was the toughest scrap he had encountered in F1, Hamilton said: "Definitely, I would say so.
"It's the same for Nico because I see his data, which makes it so hard for either of us to get any advantage at all. It would almost make sense to copy his set up. You could if you wanted to, just do exactly the same, and then it would just depend on ability.
"But I'm pretty sure we'll keep sharing data. That's how it works in all the teams. At McLaren it was the same. So that will continue, which means you've always got to keep working at getting your set-up right.
"We saw that in the last race in Spain. If you are just off, as I was, and the other guy gets it right, you see the balance changes between the drivers. That's what I've got to work on.
"Overall, though, this team has the potential to be the best. In fact we are already there, but we can't take it for granted - we've got to keep working and improving, which we will do."
In winning all five races to date, there is talk of Mercedes sweeping the board for the first time in the sport's history.
McLaren came close in 1988 when Ayrton Senna and Alain Prost won 15 of the 16 grands prix that season.