Hi Manisha,
The benefits of 360 degree appraisal over 180 degree is that in the latter, the subordinates do not have a part to play in providing feedback on the appraisal. It is only the boss,seniors,peers who are involved.The 360 degree cycle is more holistic. The subordinates also get a chance to give their inputs.
My observation has been that the 360 degree appraisal is used more for middle and senior level positions.
Regards,
Natasha