.aria files and .ariax files contain the exact same information, and are essentially interchangeable in the aria player Ensemble load menu (or by drag and dropping) They each contain the state of an entire 'engine instance' ;
.aria being a compressed binary version of a .ariax file.

.ariax are readable XML files, while the .aria files are not. The standalone player can only save the binary variant. So, for saving editable presets, the Ensemble menu should be used.

Following the original .aria files, a new .ariax fromat has been added to allow hand editing of data for power users.