The LT215/85R16 and LT245/75R16 are the same size, one is an inch wider then the other. LT235/85R16 will need the most clearance on top and between. The LT225/75R16 is the smallest tire, with the least clearance needed on top and between. All things being equal, a wider tire has more load capacity and can support the load at a lower pressure. to a point the lower pressure the better the ride - until tire failure from over flexing the sidewalls.
When I upgraded from 15's to 16's I opted for the LT245/75R16. The plan was to take 2 year old lt tires off the truck, and put them on the trailer. Then the truck had new rubber every 2 years, and the oldest tires on the trailer were 4 years.
