Well, first of all, like Sazu mentioned: They're not in the same genre.
But if you're saying which one should be the first option, I say HELLSING.
Why? It's badass. Its storyline actually makes sense. It demonstrates real Vampire-like action ... blood, gore, etc.
And unlike the lovey dovey crap, it's exciting.
I'm betting VK is famous just 'cause for having good looking kids in it. And incest ...