How do the promo versions of vampires differ from their regular in-set versions?

The Baron
AFAIK no difference.

Echo
promo is copyrighted 2004 and KMW version is 2005. Promo is also bit lighter than regular and there is little line(-) instead of point(.) in the i in Rik Martins name (illustrator)

Duality
The promo version does not have a set symbol.

Fatima al-Faqadi
The promo version of Fatima says “cannot commit diablerie.” The Final Nights version says “(Blood Cursed)”

Hannibal (Adv)
The promo version does not have a set symbol.

Hesha Ruhadze
AFAIK no difference.

Jessica (Adv)
The promo version does not have a set symbol.

Kestrelle Hayes
Promo version has wrong grouping, and she is printed “upside down” (printed with the 3E print run).

Lucita
Promo card is a millimeter longer than other cards. Promo has two lines of text while normal has three.

Marcus Vitel
Promo has slightly darker and shinier surface, regular has matte surface.

Sascha Vykos, The Angel of Caine
AFAIK no difference.

Selena
AFAIK no difference.

White Lily
The promo version does not have a set symbol.

Xaviar
Xaviar promo is published in 2002, Anarchs version in 2003. Promo also has CE-type layout and the Gangrel clan symbol is taller than in the Anarchs version.

Yong-Sun, Harmonist
The promo version does not have a set symbol.