Is It Safer to do online banking on a Mac or a Windows computer?

[Seacrest]

Forrest wrote:
...and don't bank over a wireless connection.

That's largely a myth (although I don't take any chances).
Connections to your bank should be encrypted end-to-end no matter how your computer is connected to the router.

Sure, an intruder could steal the packets while they traveled from base station to client, but they would still need millions of cycles and presumably years to break the high-grade encryption that envelops those packets.