One of the biggest differences between the LT and the ST is the amount on lubricants (used to keep rubber pliable, protect from dry rot, and increase resistance to UV for longer life) is much higher in ST than LT tires.
The reason is the assumption that LT tires would be rotated ("used") more often than ST tires (that would spend more time stored than "roaded"). Using the tire regularly circulates the lubricant and keeps the surface rubber "wet" with the lubricant that gets circulated to the surface. A stored tire gets worked less and is way more susceptible to dry rot cracks (checking). They also "time out" before the "wear out," typically, and need that extra lubricant to increase their useful life.
Many times OEM campers come with LT tires because, due to loading, a suitable ST tire is not available. You will just need to watch those LT tires for drying and cracking if your store more than you camp.
ST tires also have a different tread pattern than LT tires. ST treads are designed for lower rolling resistance and sidewall strength (for pivot turns). LT tires are designed for traction (aggressive tread with higher rolling resistance) and load bearing (less flexible sidewalls and more tread footprint).
This is not to recommend one over the other. Each tire type serves a need.
You will need to decide which type is best in your circumstance.
As far as quality is concerned both types have their own issues and vary by manufacturer and plant.
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