It's becoming a holiday tradition: The two competing high-definition DVD formats are gearing up for the Christmas season, each hoping to consign the other to the dustbin of consumer electronics and declare victory. One contender, HD DVD, has taken the lead on the hardware side, with about 58% of sales, according to Adams Media Research. Yet Blu-ray has taken a big lead in sales of movie titles. Blu-ray discs are outselling HD DVDs by about 2-to-1 this year. That's in part because so many people who bought Sony's PlayStation 3 game console, which also plays Blu-ray discs, have bought some high-definition movies.