LT tires

op wrote:
A question for you folks who have, or are going to, switch to LT tires on your fiver. Are there certain characteristics that make one tire more desirable than another or will any LT tire be fine?

It better to use a specific line of LT tires that the mfg has recommended.
Example is Michelin recommends the XPS Rib for trailer use.
Cooper recommends their HT 3 LT line for trailer service.
BFG says their Commercial T/A2.
Firestone Transforce HT.
Goodyear Wrangler HT.
Bridgestone Duravis R-250.

These tires have at least one solid rib. Some have two and others may have all solid ribs. Solid ribs helps the tire run a straight track/more lateral stability.

My fiver maxes out at 12,000 lbs. loaded so I don't need load range G tires. For that matter, does it even make sense to make that change and instead go with a top of the line trailer tire instead?

Trailer tire ?? LT and ST and P tires come on trailers. I assume you mean ST tires.
I can triple the miles and double the years in service with a LT tire. It all depends on miles of service per year.
If you make a few short trips a year the ST has worked for some.
However if your running 18k-25k miles a year then the LT would make better cents/sense.

Your trailer weighs 12000 lbs ??
If that is on the axles then the LT E at 3042 lbs won't have any reserve capacity. They will be at max load.
Now if you mean 12k minus 2000+ lb pin weight equals 10k lbs then the LT E will work great.