Popay,
Its simple...is he unsafe?If he is,then you have a duty to make your feelings known to the CP but make sure you know what you're talking about.If he is not unsafe but operates in a manner which unnerves you(you know some people get nervy when the gear isnt down and locked at 10 miles),ask him!Use the power of speech!Get him to brief you clearly.If you dont like him all that much and are subconsciously looking for any excuse to fault him on deviations from the norm,have the honesty to recognize that in yourself and store it in the database for when you make left seat.
As for direct confrontation or taking control?Not unless in your opinion he's about to buy the farm.He signed for the plane,not you.
Whichever it might be,I wish you the best of luck.