R12 is 10,000 ft. LGB or ONT were probably the nearest suitable airports to return on one engine and they were probably more familiar with LGB than LAX or ONT. Operationally it was the best choice so why make it complicated? 25L VFR traffic would not be a factor because the tower would manage that.
Smoke in the cabin would require using the nearest suitable airport as well as a single engine approach with a twin engine aircraft.