My opinion—yours may vary!
I’m not sure that we have adequately answered the OP’s original questions, so I’ll throw in 2 cents worth.
1) If you have the dealer replace the axle, you’ll get exactly what you had before, not an improvement. However, as a friend of mine used to say “Free is for me.” That is, of course, unless it is so bad that it’s worthless.
2) You are likely to get just the axle beam replaced, not hubs, backing plates, nor bearings. More on that below.
3) I’ve experienced Lippert Equa-Flex, Dexter EZ-Flex, and MORryde SRE4000. My opinion is that is the order of less improvement to most improvement. While the Equa-Flex doesn’t do much, it’s better than a solid equalizer. It would need replaced if it is visibly worn or the rubber pieces are collapsed (mine collapsed after a roadway incident.)
From the previous discussion, it appears that axle preferences are like RV brand preferences (you like the ones that have given good experiences, and …) On this forum, I believe that I have seen more complaints about Lippert weak brakes than Dexter weak brakes, and that has been my experience. The best brakes that I have experienced on 2 different trailers were ALKO brakes—but, they have been absorbed into Dexter.
One way to align trailer axles is to bend them and/or re-position the hangers. There are shops that will bend them although they are few and far between. I have had it done successfully at a shop in Indy. I talked with Lippert factory reps at a Forest River rally who stated that they will not support bending axles (risk liability, I’m sure). Their alignment solution is to replace just the beam. While hangers could be improperly located, I would bet most are pretty good due to mass production at a Lippert factory.
The systemic problem in the RV industry is being too cheap and that is plenty true with axles. We just purchased a trailer with totally inadequate axles (which we knew in advance). In researching replacement axles, I learned that Dexter makes 3 different thicknesses of 3” axle beams. Bet you don’t have to guess at which thickness was used by Brand X for our trailer. It could be that the thinnest walled beams are too light to hold an alignment either from the factory or after an alignment shop—don’t know. I replaced with thick walls, heavier rated hubs, appropriate springs, and disk brakes.