Sorry for the delay in replying, summer holiday time here in the UK. My experience is similar to your own, we find our LinkedIn community group generates more leads than the company page itself. However, there are many published examples of others that have benefited strongly from company pages. HP is one of the better known examples as they have over 1m followers. There is a LinkedIn case study on HP and also articles on the HP experience like this one http://marketing.linkedin.com/blog/what-hps-1-million-linkedin-followers-means-for-marketers on how they segment and do targeted updates to followers.
I still think LinkedIn groups are potentially better for lead generation as by their nature there is a higher level of engagement through questions and discussions.