Neo, it depends on what you mean by "best":
Best Airline- everyone has their favorite; right now mine is Continental because they actually still serve free meals on longer flights. Involves a change of planes in Houston though.
Shortest Times: Delta, American and United operate some nonstop flights on the MCO-LAX route, others involve one connection such as Delta through Atlanta or Salt Lake City, United through Chicago or Denver, Frontier through Denver, American through Dallas or Chicago, USAirways through Charlotte.
Price: Most airlines offer the same fares so it just depends on fare availability on your travel dates. And Southwest Airlines will not appear in reservation booking engines, you have to go to their website and see what they offer. Southwest flights would involve at least one stop or connection.
BobK/Orlando