I have to vote for Omerta, simply because it is a Katatonia Song and the other one is "only" a cover... A great cover nevertheless. Has s.o. ever heard Wil Oldham's original version?
Omerta, even if it sounds out of place on Viva Emptiness (this is not necessarily a bad thing, I personally find putting it and City Of Glass at the end to be a great study in contrast.)