Is a tandem axle cargo trailer worth the extra $ over single

Should be a label attached to the axle unless it's worn off or missing etc. 2 different types of axles regardless who makes them. Spring and rubber torsion. Spring suspension is obvious. Torsion, well no springs. Cummins12V pic shows what a torsion susp will look like.

If you opt for a V-nose trailer, you will gain add'l space inside.