ART Taget Adaptor - Target database options

Anyone replicating from ADABAS to Oracle?
What is your take on when to use the options “Delete before Insert”
and “Update to Insert”. Do you turn them off and on as needed?
Do you turn them off for Initial-State loads and then turn them on after
the initial-state loads are done?
Anyone see a performance hit having them on?
We had the “delete before insert” and “update to Insert” turned off and
when we did our first Replay Plog, we ended up with more records on the
target than the source.