I have been traveling for the last few weeks and I have been on quite a few flights. I booked most of my flights with Southwest except for one flight on Virgin America. After flying both back to back I had a few thoughts about the airlines.
Southwest Pros: No change fees which I love with my ever changing schedule. No fee for baggage. If you miss your flight they put you on the next one. If your flight is more than an hour delayed, they put you on any other flight of your choice. $5 drinks.
Southwest Cons: No food service on the plane. No assigned seat. No automatic check-in.
Virgin America Pros: Assigned seating which is always nice if you are late to board a flight. Great entertainment on the plane. Push to order on your own personal tv. Text capabilities to other seats. Chargers between the seats on the airplane.
Virgin America Cons: Major change and cancellation fees. Limited flight destinations within the US.
Depending on what you are thinking for would absolutely determine which airline works best for you and I have to say, I love Southwest all day and every day for their flexibility.