You can swap between them by changing the settings via the system settings bit provided you're talking HDMi and VGA, otherwise you'll physically have to change them over as you can't have both Component and VGA running as they both use the same slot in the back of the 360.
I tried this initially as I couldn't get a line output from the tv with the hdmi connected, (needed it for my sons gaming chair). When you connect the component / vga, it covers the slot for the HDMI cable.
