Q: Is there a big difference between 32-bit and 64-bit?

A: No. The 64-bit version simply allows your program to use more memory. There is no real advantage to 64-bit unless you want to fetch a one-billion-row table all into memory on your PC within a Toad data grid. Keep in mind that your version of Toad should match your version of Oracle client (32-bit/64-bit).