TJI:

Consider the multiblock read count and your physical i/o buffers.

Chances are you are going to read in 64/128/256K (or more) chunks into the physical buffers before they get passed to Oracle. The block size and multi-block read count are going to be the factors. You can do 8 blocks of 32K or 32 blocks of 8k or 16 blocks of 16k or whatever. The difference will be extremely small (I won't say non-existant) if your drive controller does 256K at a time.

Then consider the SGA buffer pool. If it is large enough (key ri tables pinned) physical io is less of an issue.

In the old days, the block size helped determine the number of data files and the database size. It also made a difference with the old, 'small', controllers and drives when RAM was expensive.

RAM is cheap. Blow out your SGA.