I recommend going weretiger on this one, presuming you mean natural rather than afflicted.
For one thing, being undead has some rather serious drawbacks. You'll lose your Con bonus to your Hit Dice, which could seriously bring your hit points down; that'll be especially bad since you'll have low hit points anyway due to your high level adjustment. Moreover, as a vampire you'll be vulnerable to sunlight, so forget daytime adventuring, any running water, making rivers a fairly serious barrier, and anyone wielding a holy symbol.
Beyond that, a weretiger has a +9 ECL, which is largely due to its 6 Hit Dice. These will help to balance out the ECL penalty, since you'll gain not only hit points, but also BAB increases, save increases, skill points, feats, and an ability score increase or two. You'll be much better prepared to face the higher-level challenges your character will be up against with that boost in power.