its not AS relevant in pro play, but still is. The old sentinels (masters 2) literally used to all use the phantom (except for Tenz who would use a combination of the phantom and the vandal). This team isn't known for the heavy use of strategy and more of their mechanics so.
when i play viper(main)/controller/sage i play defensively, taking close range fights rather than long range and FOR SHORT/CLOSE RANGE - PHANTOM IS MUCH better as you could have seen ur self in shroud's plays.
when i play duelist/chamber(which is rare) i take long range duels and hence pick vandal more.
OR(mainly attack sides)
when the entry is to be taken from long side fr. eg in iceboz b main entry, u need vandal definitely and for a site entry i personally use phantom to clear all those close angles.