Look at the mechanics of a trailer. The frame has some "give" to it, it's not noticeable but it MUST have some flex.
What do we know about Aluminum? It doesn't like to flex as much as other metals (steels) before it cracks. Welding aluminum also has a tendency to change the metal's characteristics unless it's done correctly. Featherlite addresses most of those issues quite well, that's one reason they cost more.
I know this particular part may be apples-to-oranges, but my day job I work with powersports stuff. ATV's bikes, tractors, small boats. Well it was a popular deal for a while to make the boat trailers out of aluminum. Great idea. They don't rust out and they are a little easier to pull than a comparable steel trailer. Well, what we found out is that I had to train the other techs on how to weld aluminum, had to buy a new welder (TIG), argon gas (still have mig with 75/25 gas), filler material, and a bunch of other stuff to repair them. And they break, often. Usually near the tongue area, where the two side rails meet the tongue, they crack. I've been repairing a couple a week on average and it's only temporary because they're going to break again. The other downside to them is that they're TOO light. When launching in a current, the trailer actually will float in the direction of current making it "fun" to launch or load. These are all flat bottom boats, so usually under 18' in length. Total nightmare in some areas. I won't own one. When I bought mine, I asked for a steel trailer and haven't had a single problem with it (owned it since 2012)-and I use it often.
Before I bought my enclosed trailer I shopped around. I knew I wanted a traditional trailer (not aluminum). But while shopping I found an 18' flat trailer. The floor was rotted out and I got it for $400. Replaced the floor with steel diamond tread. It's believe it or not lighter than wood and lasts forever, at least here it does....in the Salt Belt, that may not be the case (used to live there, don't miss it any). I've had it over 20 years now and it's still as sturdy as it ever was. Actually replaced the enclosed in 2009 as it was well-used and time to replace it before I had to put a ton of money into new skin. Now it's probably time to re-skin this one. Decisions decisions.
Pulling the open trailer was done for years with a regular cab 1/2 ton Ford with a 4.2L V6. Turd but it got the job done. Then traded it for a '96 with a 4.9, better but still a turd. Then a 2000 F150/5.4--MUCH better (ext cab) and still have that truck; gave it to dad. Then picked up a nice 2003 F250 with a diesel. Pulls better but diesel and maintenance costs considerably more so it washes out in the end. With the F250, it's designed from the get-go to pull a load and does it pretty good. So if you have a 1/2 ton pickup and are on the fence, you may look at a 3/4 ton. If I ever replace mine, it will be with a gas engine for sure!