I bent my axle, a 2000 lb axle, with my 1300 lb trailer. Replaced it with a 3,500 lb axle, but kept the 2000 lb springs.
With torsion, you want to be much closer to the weight of your rig. I don't know the formula, but I've seen folks posting that they used a torsion axle set up for 1200 lbs on a 1000 lb trailer.
You can also get drop axles for spring setups.
One thing about torsion axles - the suspension is not serviceable, so if the rubber (elastomer?) that provides the suspension goes out, you have to replace the axle. However, the torsion axle will probably outlast your teardrop in most cases, with proper care.