They are both really good, but phantoms are better if you're funded. However, I personally feel like NL are better for end game bosses like gollux and others because phantoms reach their full potential on stationary bosses.
Well, NL was my first class to windia also my first lvl50/70/120
and phantom is my only 200+. Pretty much was summarized^,
phantoms can definitely beat NL when it comes to funding but
for special bosses like magnus/hell gollux/CRA, NL can outdamage
us. Jump attacking is verrrry useful at those bosses and phantoms
greatest strength limits us in the mobility department. Though if
you are looking for a balanced play style(both offensive and defensive)
go with phantom. NL is easier to play at high leveled bosses though
their mobbing is meh~
I've played a Night lord for quite some time, then decided to try something new and went with a Phantom. Despite having transferred all my equips, and having a similar weapon/secondary/range, the Phantom lacked big time in damage. I also died a countless number of times while trying to boss, and seeing as though Phantoms are nothing without their buffs, I kept dying while trying to rebuff after a death. (Which may be because I only played it for 2 weeks and didn't get use to the play style) But yeah, in my opinion Night Lords are a hundred times better.