I read that ST tires are better for trailing than LT tires for a couple of reasons:
1. Are rated for holding a heavy load for long periods of time
LT tires would be too. A heavy vehicle is a heavy vehicle, whether it's a truck or a trailer.
2. Have more plies in the size walls for impact resistance
Possibly. I don't know. CapriRacer is the expert and I'm sure he can say. I suspect that this isn't a blanket statement you can apply across the board.
3. Have a different rubber compound to resist UV light decaying the tires
I have heard this too, along with a compound designed to sit idle for long periods better than LT tires. That is the theory, anyway. From a practical perspective, you have this standard more in tune with a trailer's needs, however, you get for the most part, ST tires made by a second tier brand at best (save Goodyear). No R&D money sunk into this market. Manufacturing in China for 99% of these. Poor quality control. High failure rates. Speed limited to 65 mph, leaving little to no margin for safety on the highway.
Or there are the LT tires. From a load perspective, they are almost the same as an ST tire. Sure, you lose the advantages that exist in theory. CHoose a good brand/model (and there are quite a few), and you gain, a market where there is ongoing R&D, the availability of tires made outside of China, many made in the USA or Canada. Good quality control. Failure rates that are much lower compared to ST. Speed ratings on many of these, giving you a safety margin.
On top of that, you get better availabiliy, often better pricing and mostly radial choices. The UV resistance? Cover your tires during storage. Besides, what about all the light trucks these are mounted on? They see the sun too. And these need to be replaced in a 6-10 year time frame anyway, whether they are ST or LT. Idle for long periods? So you have "square" tires for the first few miles after a long park, big deal. And if you tow lots, those are moot points anyway.
For me, the replacement choice is very clearly going to be an LT tire.