An exemplary adaptive Hypertext Transfer Protocol (“HTTP”) media streaming system may be configured to stream a media program from an HTTP media streaming server subsystem to a client device during an adaptive HTTP media streaming session in which predefined segments of the media program are progressively downloaded from the HTTP media streaming server subsystem to the client device by way of a network connection. For each next predefined segment of the media program to be downloaded, the server subsystem may dynamically select, based on one or more of the exemplary factors disclosed herein, a version of the next predefined segment of the media program from a plurality of versions of the next predefined segment of the media program and download the selected version of the next predefined segment of the media program to the client device. Corresponding methods and systems are also disclosed.