Manipulating Large Object datatype in Postgresql

Hi,
We have tables with data type CLOb and BLOBs (in oracle). This needs o be migrated to Postgresql. What data types can be used for this. I've done some resaerch/search in this and found that (correct me if Im wrong)
1. For CLObs the equivalent are TEXT and OID(lob).
But streaming(thro' jdbc) is possible only with oids
2. For Blobs the equivalent are oid(lob) and bytea (again straeming is possible only with oid)

Questions:
1. Which is the better approach for CLOb/BLOB? I need straeming possible since the data are pretty big
2. How is UPDATE/DELETE handled with the lob datatype?

Would it update the referenced data?  Or would it create a new lob
and update the pointer, keeping the old data somewhere?  Or would that
depend on our implementation?  Would it make a difference if the new value
was null?

Thanks