Hello Gopi,
The reason to go with Standard deletion approach is mentioned below:
1) Events which are in invalid status will never recorded in /SAPTRX/EVM_UNPR table and never be picked up by report /SAPTRX/DELETE_UNPR_MSG (This is one of the requirement of Dipak to delete failed messages too)
2) /SAPTRX/EVM_WRITE program only delete entries of processed messages if those messagres are not linked to any event handler (So saying it will delete all processed message irrespective is not true). All processed messages are only eligible for EVM_WRITE if respective event handler is deleted from system, which means the event messages are irrelevant and ready for deletion
3) SAP never recommend to use /SAPTRX/DELETE* program in production system and use archiving deletion (Even if you dont want to store archiving files)
Hope this explains now.
Regards,
Kinjal Rathod