Metrics for comparative study of collaborative systems

I have a collaborative computing platform which I want to run a user study on, and compare it with an existing, paper-based system. Both systems are meant to be used in some specific types of meetings (e.g. brainstorming, ...). This is done for an academic publication.

My approach would be to run user studies and evaluate a set of metrics and then compare those metrics. More concretely, I think it makes sense to compare these two different approaches on a per metric basis, and finally come up with a table, with the mentioned metrics as rows and each system as columns.

The question is, what such metrics would be? Is there any widely accepted set of parameters for such studies? Any pointer would be highly appreciated.