Wireless B is 11Mbps, wireless G is 54Mbps. As long as you have a decent wireless connection to the router, neither would really make that much of a difference, but I still wouldn't buy B.

An alternative to wireless encryption (WPA/WPA2/WEP) is to use MAC filtering. It basically allows only specific hardware to connect to it, and you can have an earlier wireless encryption on at the same time. It is possible to spoof the MAC address of hardware, but anybody who knows how to do that is probably using their skills for something more evil.