Questions such as this are very difficult to answer because they assume a direct correspondence between writers and the characters they depict. Most often, one cannot easily say whether or not the author is most associated with a particular character. All of this being said, one could argue that Voltaire's philosophical views tend to run along the lines of Martin's.
Pangloss's philosophical optimism, particularly its adoption of a fatalistic, passive attitude toward the world, does not appeal to Voltaire. Voltaire spends the majority of the work ridiculing this philosophical perspective, specifically its tendency to deny empirical evidence. It is essentially not a philosophical system that has any relevance for the world, for it is not informed by experience in the world.
Martin's philosophical outlook, though somewhat gloomy, most closely represents Voltaire's own because of this thoroughgoing "realism." Martin, unlike Pangloss, draws his conclusions about the world from the events around him. He does not stubbornly adhere to a preset philosophy. Martin wants to display for Candide the misfortunes of the world in an effort to "bring him around," in the same way Voltaire wants to show the reader the ridiculousness of philosophical optimism as a viable perspective.