Each is a different polarity, so you'll probably want to use both sides, unless you're going for one specific channel, or group a channels that use the same polarity. You can combine the both into a standard old DTV-Style 3x4 multiswitch (very cheap!) and then you'll have both polarities from your LNBF and be able to connect to 4 receivers too!
A 3X4 Multi-switch or a Diseqc switch? I have the Diseqc 2.0 switch in front of me now, would that work?