Objectively, you can't just compare WN's on time stats to the other legacies. Considering that a huge percentage of domestic flights marketed by the legacies are actually operated by their regional partners, you also need to take into account the on time stats of the regional partners... which are often much worse than their mainline counterparts.
I agree with this.....also the legacies routing structure is different.
Their regional partners are generally flying betwwen hub and a few cities back and forth over the course of the day.
Southwest on the otherhand has a highly linked flight network which can result in more delays.
In the OPs situation ----where was the plane coming from?
Some of the planes say out west but there area a few planes that do back and foirth cross country routes.
For example if the day's itinerary of a plane was:
PVD-BWI-TPA-BNA-MDW-OMA-DEN-SFO-LAS
If there is no delays everything is fine.....but given there are 8 chances for ground delays due to weather or traffic or some mechancical delay can easily add up...20-30 minutes here and there suddenly puts the flight over 2 hrs behind schedule near the end of its trip.