Every one of our customers who has access to our API demonstrates that the Ark (YC W12) API has much more data than FullContact's API. Send me an email and I'll hook you up.
We always encourage potential customers to try other services. With over 500 paying customers of the FullContact API from some of the internet's largest SaaS providers, we're pretty confident in the quality and quantity of our data.
Bottom line is, none of us will have the same amount of data as Rapportive, because Rapportive had direct access to LinkedIn's data warehouse. (And as we all know, LinkedIn has never been shy about hoovering up data from anywhere it can get it.)
I just requested beta invite on your website but didn't see your contact details (mine are in my profile).