In my opinion, if you want to go Magic-heavy in your Lord choices, there's very little point paying extra points for combat potential you aren't really after. Furthermore, once you start taking some of the best magical items (such as the Black Periapt on your Lord choice, and a Scroll on a Hero wizard), you don't have enough points allowance left to get all the gear and upgrades that make combat vampire Lords so scary. As a result, you have a wizard who is overcosted for his wizarding potential, and doesn't really pull his weight in combat either. Like many things in Fantasy, you want to be at one extreme of the scale, and having something in the middle tends not to work. Mannfred Von Carstein is a decent choice if you're aiming for a mixture of both though.
If you're going Magic Heavy, a Lvl4 Necromancer with the Black Periapt and the talisman of Preservation, bunkered in a big, 5-wide unit of Skeletons with full command and two Tomb Banshees (hence pushing the Necro to the second rank) is the way to go, in my opinion. A cheap Vampire/SGK is an option to act as your general and hence allow your Necro to take Death. I'd then get two-three hero Necros on a mix of Death/Vampires and maybe grab a couple of the nice Arcane Items the
VC have to offer.
That's not to say that Magic Vampires don't work - they certainly do - it's just that you're better off simply loading your Vampire Lord up for combat and then upgrading him to a Level 4 and maybe giving him the Earthing Rod too. This still gives you an all-important Lvl4, but it's not really "magic heavy" and the Vampire Lord itself is certainly far more geared up for combat.
Ultimately though, it depends on your playstyle and what you want to get from the army. It's certainly worth seeing if you can play a few games with both builds (even if you have to proxy Necromancers and the like), to see which one you prefer.
Hope this helps, any more questions just ask!