The Stud comes standard with the Timbren 3500HD axles.

The Timbren can be added to the Colt and Colt-L’s for $625 extra.

Timbrens certainly ride smoother and give you more ground clearance, but they will require more servicing - particularly with the rubber bushings. Also, alignment on Timbrens aren’t as straight forward as straight axles. Warhorse aligns all Timbren axles, but variations in Timbrens manufacturing tolerances can prove tricky. Regardless, Warhorse trailers aren’t semi trailers and slight imperceptible alignment variations will not cause wear issues on the tires. 

If you are very sensitive to ride quality and want the best ride possible, get the Timbren. The Timbrens are not tougher than straight axles - ride quality is the only selling point.

Also, ground clearance is a moot point - your vehicle’s rear differential is the deciding factor of if you’ll clear an obstacle, not the trailer’s axle.