Perez is faster faster than Rosberg on outright pace. So he could go to the cleaners with Hamilton some races.+1 for Perez - he seems to be in the sweet spot. Reliable driver, will bring home gobs of points and podiums, but Hamilton should be able to outpace him to the point where there won't be any real championship drama.
That's a recipe for a happy garage - team gets their championship, Lewis gets his, Checo plays the amiable "just happy to be here" role.