This is one hell of a complex equation, that if you're looking for just "who's the awesomest dude in space"... it could take an eternity to figure out.
Each has serious awesome points going for him.
Both led sci-fi series that we cut short way too early.
Both captained a crew of badass motherfuckers and unstable weirdos.
Both are happy to gun in the face of any jerk who's stupid enough to cross them, and go out of their way to make retribution a painful and creative process.
Both are surrounded by mega-hot space babes.
Both have on multiple occasions hit cakes with mega-hot space babes.
Both have amazing timing for one liners and badass commentary.
... I could go on for hours in this way.
But Mal is the Han Solo type space cowboy, and Crichton is the bad mamma jamma starfucker extraordinaire.
Hmm... it may depend on scope. Mal has a rag-tag band of expert rebels and thieves and a ship that flies on a shoestring and a prayer, and yet manages to defeat the powers that be. Crichton has a ragtag band of expert warriors and criminals and a stupendously badass living ship that is piloted by a muppet and yet can never quite manage to defeat the powers that be - which are admittedly severely more formidable than the system government that Mal and the crew of Serenity face.