From a marketing perspective, I would say go with TechCrunch. Their website reaches 3.9 million people monthly, as opposed to VentureBeat which reaches a little over 500k monthly.

Personally, I still say go with TechCrunch. :-)

Hope this helps.

While both are highly respected and I am a subscriber to both, I tend to think that TechCrunch has the better brand. I say this because they are often times the first to post news and often have substantial facts to back up their news. Also, they often have excellent and highly qualified people guest posting for them and offering excellent features and commentary - as well as a high profile community of commentors as well.

As opposed to banner options, have you considered more targeted advertising alternatives? Such as Google Adwords or Facebook Ads?