The bcmwl5a is the newer of the two drivers. I'd try that first and then use bcmwl5 if the 5a doesn't work. Be sure that both the .inf and .sys files are in the same directory when you run ndiswrapper -i, as the .sys file has the actual drivers.
And just so you are aware, there is a native linux driver
project for Broadcom chipsets like yours. I've given it a go and it currently is of limited use (no WEP or WPA support as far as I can tell).