here's a pic of my harbour freight cheap chinese POS trailer.
Pro's=cheap
Cons=I had to assemble it, very lightweight steel construction, total piece of junk.
Pro's- its so trashed I can chuck logs at it all day long, I don't know if I would do that with a plastic trailer.
Cons-rear gate total garbage-complete joke- destroyed already.
The biggest problem with these types of trailers aren't just the trailers- It's the cheap chinese tires that come with it. I upgraded to CARLISLE tires- and spent more on the tires than the trailer itself. The chinsese tires WILL fail

so be ready to upgrade!
If I had to do it again-I would go craigslist and try to find an old John Deere trailer (1960-1970's vintage)- They all rust- but even after the rust- the JD will have a thicker metal gauge and be much more robust. If will not crumple like the tin can this thing is.
Either way- count on tires (the chinese ones suck, the used JD (or some other equivelent quality brand ) will probably be dry rotted.
Storing outside- All trailers will attract wasps nest with equal ability~
The steel will eventually rust, but wont the plastic eventually harden and crack? Again- I am more concerned about the tires dry rotting outside than the trailer itself.