write optimised DSO and PSA

Hi Gurus,

I have alittle doubt regarding the write optimised DSO.

Its understood that we r using this W-O DSO in the staging layer .( from Datasource (PSA)----> DSO). Its used for huge no of data and as it has only active table and no SID ... performencewise its good to have.. and also we need to delete the older data for the space in the DB table.

As the same thing we can get in the PSA. As data is also loaded on request level.. and we can delete after certain period of time say 7 days.... and to get historic data we can maintain a standard DSO with full load.

Then why to maintain WO-DSO in the staging layer