It really depends on the unit. Some TT's ride lower, but most all 5th wheels ride higher than TT's and some even higher yet. Depends on the frame size, tire size and how the axles are sprung.
With TT's some have the axles under the springs, some over the springs, some on 14"-15" or 16" tires.
My last TT and current 5th wheel are almost exactly the same for ground clearance. Same frame size, same 15" tires and the same 3 steps to get in.
You really need to narrow down what units you're looking at and then see how each is assembled.