Hi Ricardo,
It will depende of how much details do you want to explicit at your diagrams. For a higher level design focus on initial architecture, you can depict your diagrams using only collaboration techniques. Note that you don't need to use collaboration diagrams for this, the collaboration techinique is about the emphasis on which responsability belongs to which object.
Thanks a lot for your advice!
I agree with you that the collaboration diagrams can bring more value than sequence diagrams at the architecture level. The collaboration diagram seems to me like a natural extension of the component diagram.
Regards,
Dan