you can lift the front with the t bars but you lose suspension function.
from
San Diego Off Road Innovations LLC
Torsion Bar Adjusting and the Affects Thereof
To summarize the difference from the vehicle driver perspective between 1.5" of ball joint spacer lift and 1.5" of torsion bar adjustment lift one could say that ball joint spacers make for a smoother on road ride with more off-road suspension flex and corresponding capability.
To understand why this is, it is first helpful to understand why it is the vehicle ride becomes harsher the higher one lifts the vehicle via torsion adjusting. The first reason relates to down travel and is very straight forward while the second, relating to the effective radius, is less so.
Down travel: You need it
Quite simply, when one of your wheels encounters a depression in the road such as a pothole, one of two, or a combination of these two things are going to happen. The truck’s wheel will enter the hole while the chassis remains relatively settled. Or, the truck will fall into the hole which will unsettle and jar the chassis (and occupants). For the wheel to travel downwards there must be sufficient down travel to do so. When you adjust your torsion bars for lift, you sacrifice down travel for up-travel. You can absorb a larger bump but if you encounter a pothole type of depression, the vehicle falls into the hole with the front wheel often impacting the upside on its way through. This is very hard on the vehicle and occupants. The results are a poor on road ride.