i dont know which one will be better,but bloodlines have much much more replayability since hl2 is a linear and only 20 levels fps...bloodlines is a very open ended rpg with a lot of races to play...not races ,clans.
i remember the guy from gamespy went apeshit when he saw the demo at e3,he said that the curtains and lamps hanging from the roof move in a very real world way,so to all the nayseyers:get ready!bloodlines is coming for you!