Ok, here goes:
-
VC are considered to be a stronger, and more balanced, book, overall.
- When the
VC General dies, your army crumbles. Once. If you have another Lore of Vampire caster, you stop crumbling until they too die. On the other hand, if the
TK Heirophant dies, your army crumbles and there's nothing you can do to stop it. However, as
TK units'
Ld is higher overall, they don't feel the effects of crumble quite as keenly.
-
TK are very shooting-orientated. That's not to say they can't do combat well (and they can), it's just that
VC have literally no proper shooting, whereas
TK can viably field an entire ranged army.
-
TK's magic is stronger (though
VC's is still good)
-
VC can resurrect models much easier, including bring whole new units into play
-
TK cannot march (ever), whereas
VC can do so if in range of the General (and certain units can all the time), making
VC faster. Note the comparative.
VC really aren't fast, just
TK are even slower!
-
VC have a much higher abundancy of Ethereal models
-
VC have much stronger combat characters, some of the best in the game. The Tomb King ones are still decent though.
- Speaking of which,
TK Princes and Kings pass on their unmodified
WS to any unit they join, which is cool.
-
TK have units which can "deep strike"
-
TK have chariots (and can also make entire armies of chariots) and war machines.
VC do not (really)
-
TK's monsters are Necrosphinxes etc, and
VC's monsters are Terrorgeists etc. They're two very different kinds of monsters.
-
TK don't like fire.
-
TK's Special Characters are actually pretty good, on the whole, whereas
VC's aren't, really, except for perhaps one.
-
VC have cooler magic items
Quite a few differences there, some of them minor, some major. Hope it helps!