Timbren 3500HD axles are middle-tier axle systems. They are smooth, easy to work on and very simple. 

Timbrens ride 30-35% smoother than straight axles. 

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.

If you want brakes with your trailer and you select Timbren, it's worth looking at the CRS2 suspension, which is a premium suspension and comes with brakes. The CRS2 is only a bit more than Timbrens.

If you want 33'' tires with the Timbrens, the 65 gauge bushings must be installed to ensure the tires don't rub.