A pro I watch basically explained a preference to the phantom like, the time to kill difference between the two guns is so small that the determining factors are actually things like crosshair placement preaim/who has better information, peeker's advantage, and other strategic factors. Given that's the case, he and his teammates almost always choose the phantom since being able to safely prefire into smokes is a huge advantage if the enemy team has a Brimstone (which at the high level they always do). He chooses the Vandal situationally when he is planning to play at a long range with ADS and tap as a more flexible alternative to the operator. This is from the top tier of Valorant rank where everyone has amazing aim and strategy so his perspective may not be completely applicable to lower tier but that's the basic justification for the Phantom. The player is ScreaM, he was a two time top 10 ranked CSGO player and now mains Sage in Valorant