The op is asking about 15" tire sizes for his smaller size trailer. Assuming his OEM tires are ST225/75-15 D at 2540 lb per tire he sure don't need a G tire a 16" G tire at 4080-4400 lbs capacity.
The new Endurance would be a good pick even though they have only been out just under 2 years now. MILes and years of trouble free service will tell the long term story.
Another excellent ST class tire used mostly in the commercial hauling world is a Provider ST tire. They're one of the first new gen L and M speed rated ST tires and have been around since the '10 era.