SQL & PL/SQL

Dear Gurus,

We have a requirement to loop through few thousands of rows and do some complex calculations ( We have to do it in PL/SQL as it wont be possible through simple SQL). These rows are output of a long running query which will process millions of rows.

Now the issue - our team is having a confusion whether we should use Temporary table or Two dimensional arrays.

We have tried in both the ways and as of now there seems to be not much difference in processing time. ( I know it is not good to rely only on processing time, specially when it is just a testing environment - not as many data as in production , diiferent server, ....)

Could you gurus please thow some light on this? Will the memory usage and other resource usage be same in both the cases?

Thanks in advance.