Use the handlebar switch to shut down the engine. In my opinion, using the compression release to stop the engine eventually carbons up the decompression valve and it will be one more thing to deal with on maintenance.
The reason mopeds in the U.S. have two engine stops is that the government thought people were too dumb to figure out how to stop the engine in an emergency.
But if you have two, doesn't that make you think which you should use?
Use the decompressor to start and the handlebar switch to stop.