My first utility trailer was a 5x8 open. It served me well for many years.
My second trailer was a 7x16 open. It has met my needs. It can carry a Polaris Ranger Crew with snow tracks on. This trailer has been broken by hundreds of miles on Forest Service roads requiring some rewelding. An aluminum trailer would have been destroyed.
My third trailer was a 6x12 enclosed. Big enough for a few jobs; good enough to keep when I don't need the big trailer but quickly outgrown.
My latest trailer is an 8.5x24 enclosed with 7' internal ceiling. 14k gvwr (4k lbs empty) is overkill, but I would rather be safe than sorry. It is big enough for the Ranger plus a bunch of stuff I use for my hobby. This trailer is an H&H. I understand that they tend to be heavier than other trailers of a similar size, but I suspect they are overbuilt (ok with me).
Lesson: big enough rarely is.