As I have already written to you privately, the Amigaos format is designed only for Workbench systems on Amiga while the WHDLoad format is much more versatile and useful for a variety of real/virtual/simulated Amiga environments and machines, such as the 500 mini ed PC/Linux frontends such as Hyperspin, LaunchBox and Batocera.
Furthermore, it is ideal for those who - even in the Real Amiga with Workbench environment - already have a collection of games in WHDLoad and would like to add your game to the catalog while maintaining the same standard: as already said in private, the choice is yours, however think about it; )