Temporary table vs pl\sql table

Hi , I've a process which need to do a lot of processing (summaries) on a large 
set of data.
 
The main flow is as follow:
 
   copy the new rows since last run (up to defined row count) to a temporary 
table.
   Run various selects with group by on the temporary table and merge them into 
summary table.
 
 I wander (I will conduct some tests ofcourse ) what type of temporary table 
will be better:
  
   1) create ... temporary table or ...
   2) create type test is table of  
 
The first option has more i/o and go throw the buffer cache , but doesn't 
consume a lot of memory
the second option doesn't has I/O but consume more memory for the PGA.
 
Any ideas ?

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