"Most deserving" is SO open to interpretation though. It leaves the door open for teams to get in for all sorts of reasons that have nothing to do with basketball. Davidson this year, for example, hasn't proven it on the court. It seems awfully easy to go down that road and end up picking teams based on what kind of TV ratings they'll bring or how well their fans will travel.
"Best" is of course also somewhat subjective, but for the most part we all understand what "best" means even if we may not agree on who the "best" is.