I have always loved the iconic look and design of the military quarter ton trailers. That being said, after using more than a few I don't like the tub size and would always go for something a little more practical. I use 4 x 8 sheet goods as the go/no-go gauge. If you can't carry a sheet of drywall safely, I believe the trailer is too small. My personal minimum size for a little trailer would be something like 4' x 6' to 6.5' with 18" straight sides and a flat, floor level tailgate. 4' x 8' is even better.
Back around 2006 or 2007 I bought a M101A1 from govliquidation.com and didn't realize it was less than 48" between the fender wells before I bid on it. Very frustrating to have a trailer so big and heavy that couldn't carry sheet goods flat on the floor. I swapped the military axle and brakes for civilian stuff to lose some weight but it still scaled out at 1K lbs empty and was honestly less useful than a cheapie Harbor Freight folding trailer both on and off road.
Even if you never haul sheet goods, 4 x 8 capacity is a good minimum standard as that will carry an ATV, 2 dirt bikes, most street motorcycles, a washer and dryer, 2 pallets of anything, a sofa, one quarter cord of firewood, a cubic yard of dirt, cabover truck campers, etc., etc. Even just camping gear can really gobble the cubic feet; take a look at photos of M416s in action on this site and you will see what I mean. My coulda, shoulda, woulda is don't be afraid to go a little bigger on your trailer.