Straight, with the elbows inline with the upper chest/neck. Touch the DB's together at the top. Sort of a crossover effect, a little more tension on the pec's. If you wish, draw up the knees above the body. Eliminates most back arch or body English. More focus on the pressing muscles. Full stretch at the bottom.
Big Dawg version: Semi straight grip, with the ROM directed to the middle portion of the DB press. Like never locking out or hitting the bottom/stretch of the exercise (TUT). Feel free to cheat during the process.
Of the above two versions, pick your own poison to see which works best for you. Good Luck.