You mean about the typing of the character Nathan Fillion plays? I'd say it's very difficult to make an assessment, because the series doesn't seem to have been written with archetypes in mind. Once you're aware of Myers Briggs you can often pick out which book authors and television script writers are keeping a defined personality type in mind to make their characters "ring true." "Firefly" is a space western, almost literally, and what they are keeping in mind is the appealing nature of characters from the old westerns. You could take an episode of "Gunsmoke", "Wagon Train," "Bonanza", "Cheyenne," "The Rebel," "Sugarfoot," or movies like "The Good, The Bad and the Ugly" or "Stagecoach" or "Fort Apache," drop the characters from "Firefly" in it, and they'd all sort themselves out into the various roles. Note that Malcolm, much like John Wayne or Clint Eastwood or Robert Mitchum, sometimes expresses anger, but never blusters or trash talks. Compare that to characters played by the newer generation of mostly-just-violent screen heroes like Stallone as Rambo, Bruce Willis in the "Die Hard" movies, etc. Rambo, etc, are hard all the way through, unlike Fillion, who is just hard on the outside and has some ambiguities in his life in regard to people like courtesan Inara Serra. Having two-dimensional characters instead of the usual one-dimensional characters may have been a reason the series didn't catch on with the general population; even that much is too complicated in a society dominated by people quick to make judgments about courtesans and other things that don't fit established patterns of respectability.
It is interesting that Fox television, as opposed to Fox News, seems to have programming that invites you to be tolerant and aware of life as an ambiguous place. "Bones," "House," "Glee," "Fringe," etc. In some of those, Bones and House particularly, you can almost see the Myers Briggs text leaping off the pages of the book as the characters perform. One of the curses of awareness of type is the need to deploy "willing suspension of disbelief" for yet another facet of entertainment.
Or did you mean "is he cute?" Ladies seem to think so.