Lucemon has mastery over darkness while most of Vegeta’s attacks are light based. It’s a nice contrast in their moveset, but at the end of the day the critical factor here is simply that Vegeta is way more powerful than Lucemon. Lucemon can’t hope to grasp the limits of Vegeta’s powers, nor would he stay in the match long enough to truly comprehend them. A Saiyan is simply not to be messed with. Vegeta wins.