The main asset of weight-shift control is simplicity. There are no control lines to route, no bellcranks or hinges to hang, and no barn doors to swing. If you do force a stall, just a slight drop then a yaw occurs, not a spin. The weight and balance on a trike is not critical. The wing always flies at the proper angle of attack no matter how you load the trike body.
Rough field landing capability is better than almost all ultralights.
The high ground clearance and fiberglass suspension make more fields avalable for landing. You can't keep a trike wing stalled. When you stall it, the trike nose falls forward and the wing starts flying again. Without a tail, a trike weighs less and will have more performance than an equvilant three-axis machine. The high aspect ratio makes a trike a better glider than most ultralights.