It depends...
If you primarily do off-grid/wilderness type camping, it's your preference. However, if you primarily camp in developed/pay campgrounds, the awning needs to be on the passenger side. The majority of all pay campgrounds in the USA are setup for left side=utility hookup side, and right side=patio & entertaining side. Just take a look at any Motor Home or Travel Trailer.
If you're using a small off-road trailer to camp out of, it wouldn't really matter even in a pay campground, because you can disconnect and position it any way you wish.