As you have read... Both are excellent gliders.
Owned LS4 for 7 years (and LS6 for 12 years) so would be one of the happy returning customers Hr. Weber bought LS for, until DG's customer appreciation policy AKA "LS Tax" came about.
LS4 is one of the easiest gliders to get performance out of, it pretty much does what you're thinking. The 20 is a great performer, and I prefer having that extra handle.
Replacing the gas strut on the gear is like replacing the gas strut on a car's hatchback. Regular inspection, occasional maintenance.
Brakes in either LS4 or early 20 can be fixed, ie Vintage Brake in Sonora, CA. or the various disc brake mods available.
The Klappi trailer is probably only a factor if you've previously used one, sort of like automatic control hookups: What's the big deal? Oh, THAT's the big deal.
Jim