Hi Bachus
The Wersi OAA can play all Yamaha styles without conversion, (No external software required) and in most instances sound better on the Wersi due to the sound system. (The Yamaha sound system tends to compress and round off the sounds)
EMC Styleworks is fully integrated (You would not know if it was not mentioned in the manual) into the OAS system (It just requires activating) which means other manufactures styles can also be converted. (Due to the integration, the conversions are far superior to the software alone) In addition the OAA can display and use all the variations/ fills etc that are available on any other instrument. (These are automatically made available when the converted style is selected)
Hope this helps

Bill