Forgot to talk about open or closed.
Open easier to load/unload, open sides easier to grab things faster from any side.
Hauling debris, mulch, top soil better with an open trailer.
Weighs less save fuel, doesn't block your mirrors easier to see behind you.
Closed gives security of locking up your trailer but people can break into a shop, your home garage, or trailer if they want to bad enough.
Equipment stored out of the weather when you don't have garage space.
Some want a closed trailer to have a 5 gallon pail/porta potty.
Thing I like about having a an open trailer there is no excuse to not clean the mowers at the end of the day because the open trailer has to be unloaded and the equipment put into the garage.
There are the lucky ones that have a garage large enough to park their loaded open trailer in their garage.