A friend of mine has both a Phantom and a Vector arm on a table drilled for two arms. He has both a Titan i and a Transfiguration Orpheus cartridge. Both cartridges sound terrific on either arm. I would characterize the Phantom and the Vector as very well dampened arms -- the arms control and dampen vibrations imparted by the cartridge. This is quite evident by the fact that with either arm one hears very little "groove chatter" coming from the arm/cartridge combination. In this respect, the Vector is slightly quieter than the Phantom. Is this good? In theory, yes, but in practice it depends on one's taste and system interaction. In a slightly dead (or "polite") system, it may be an advantage for the arm/cartridge combination to resonate and "sing" a little. This can make the music sound more dynamic and alive. I've clearly heard this in this same system when a Linn/Naim Aro and Transfiguration Phoenix cartridge was auditioned.
As far as objective performance, with the Orpheus, both the Vector and Phantom tracked a Shure Obstacle course record with equal ability. But, in terms of tracking, both were clearly outperformed by an SME 309 using the same Orpheus cartridge. Still, in terms of real life performance, all of these arms performed well.
I have seen many topnotch vinyl systems built around a variety of arms/tables so I can't say any one combination is obviously superior. I've heard great systems with Vector arms (my own choice), Grahams, Triplanars, Shroeder, Naim, Clearaudio and Moerch.