Peer-to-Peer Networking question

I have to connect two computers in my house; one is upstairs and the other is downstairs.

How should I do it? Running a cable? Or should I purchase a wireless network.

I want to connect both computers because I am putting a cable modem on mine to access faster Internet connection speeds.. By connecting both computers we will have both computers connecting to the Internet via cable modems.

Any suggestions? If more information is needed let me know.