I find that flights to and from MSY vary quite a bit depending on what is happening in New Orleans. Conventions, football games and Festivals all happen frequently and can cause an unexpected change from what is "normal". People are often not aware of large conventions that are in town, 25,000 orthodontists can make a pretty big impact and no knows when they are there except maybe some on the hospitality industry. That said I don't have a lot of experience with PHX