In the first one, the switch and PIR are wired in series.
-Switch on, PIR activated = lights on
-Switch on, PIR not activated = lights off
-Switch off, PIR and lights off
-Switch off/on quickly, PIR goes into permanent ON mode, until you switch off/on again.

In the second one, the switch and PIR are wired in parallel.
-Switch on = lights on, regardless of PIR activated or not.
-PIR activated = lights on, regardless of switch on or off

Downside with the second one is that you can't switch the PIR off if you don't want it to trigger for some reason.

Hope this helps, and that I understood it all ok.