Simply put, it allows more clearance, as the torsion bar that crosses from side to side is higher than the center of the wheel. Each wheel then moves separately in up and down movement depending on what it encounters. So your trailer does not tilt as much as a straight axle and leaf springs would make it tilt.
So axleless Timbren style means resisting a pretty substantial twisting load.
Tube axle and leaf springs apply a pure vertical loading.
Twisting requires considerably more steel than a pure vertical load and a bit more engineering to get it right.
Tube axle, leaf springs are a no brainer.
Before investing too much, check the trailer load rating, it looks pretty light.
And add up the stuff you want to load.
I'm thinking that trailer might be easy to overload.
You overload an overland trailer and something will break.