The answer to this question depends on which project you wish to run.

Choosing a distributed computing project is a personal decision. BOINC is not a DC project, and not all distributed computing projects run on BOINC. You should research the various distributed computing projects and the various DC forums here at BBR to find a project you are comfortable with. The DC project you choose will dictate whether or not you should install BOINC.

Some DC projects only run on BOINC, others only run on clients dedicated to that project and yet others give you the choice to run either a dedicated client or BOINC.

Resources:

Distributed Computing Clubs at Broadbandreports.com

Active DC Projects by Distributed Computing Info

How-To: Join Distributed Computing projects that benefit humanity

List Of Distributed Computing from Wikipedia