Hi.

It seems that a combination of both approaches with the right dose of each, could be best. 

The self assessment can be personalized in your own expectations or to fit your organization expectation, but peer group attempt to recall the entire critical situation how you are and they focus on common themes of high / poor attitude, behavior and your performance etc., throughout the year

 External peer group evaluation will reduce the bias

Both Self Assessment and External Peer Assessment are important for maintaining fairness in performance management.

I think all of these is important. So, it is very difficult to specify.

Dear Avishag Gordon Madam, Kalaiarasi V  Madam, Respected Subhash C. Kundu ,

Dear Niranjan Biswal  Sir, Dear Chalamalla Srinivas  heartiest thanks for your valuable feedback...

Both Assessments  are require for quality works..

Dear Ramdas Sir, Heartiest thanks for your valuable feedback.