As with most things, there are polybushes and there are polybushes..
I'm pretty sure I'm right saying they have improved a lot in the last 10 years or so... and a better understanding of the grades of urethane to use.
Some of the mfrs offer a variety of hardness ratings, and especially design specifically for leaf spring applications.
I cannot find much independent info on poor wear or low life.. quite the opposite, with most mfrs suggesting 6 to 10 times better life. But they would say that...
One problem that's pretty obvious is poor fitment, they need lube when fitting, maybe plenty of it, and Brickyard's Powerflex ones come with this in the kit, much like copperslip. Some designs may not fit that well, or even be designed incorrectly; but the main thing as with most rubber/flex bushes is to mount them unloaded in the car's basic suspension setting, that is, only nip them up properly only when the full weight is on the suspension.
The big question is, in suspension LCA applications, should they twist like rubber or should they spin in their housings?
Some slight uncertainty there.
I can't necessarily agree with Andy that most of the rubber bushes on the T25 last 15 years, they might look like they do, but take the big front radius rod ones, they usually look fine, but just take them out and see the fretting inside against the spacer tubes (that usually have rusted to pieces, anyway) - replacing those with new rubber ones def. makes a difference after 15 years!
And T25 and esp, Syncro LCA bushes are well known for shuttling forward or rear in the housing, possibly due to bad fitment, possibly a life problem as they harden and shrink. This upsets the steering geometry badly. And replacement ARB drop-arm rubber bushes usually last 5 minutes... as was said above.
Anyone who knows Jaguars, the original XJ6 and XJS particularly will know that fantastic quiet, low NVH ride comes at a cost!
A very expensive replacement of dozens of rubber bushes about every three or four years! Don't change them and the cars becomes abominal, uncertain sloppy steering, bump-steering and then eventually banging and knocking as they pack up totally... but then, some seem totally immune to such things
Fit hard polybushes (racing style ones) and NVH will approach that of metallic rose-joints; hopefully all the ones avaialble for T25s are a suitable compromise. The rack ones certainly tighten things up nicely, with a very slight increase in NVH I'd say. Can't see any problems with the ARB polybushes either.
But time will tell, with the LCA ones...