Well, neither really improve the handling, per se. They do change they way you feel the road and how quickly input and feedback come and go between you and the road.
Racks tend to have very precise steering response with very little slop, so they do improve the road feel considerably. Since this is a kit that hangs off the stock mounts, I would be concerned with potential deflection eliminating the precision that comes with a rack assy. Also with racks, the potential for bump steer is possible because hte rack pivot points may not match the stock pivot points. Unisteer says they have this fixed, so it may not be too bad with their unit. Regardless, it would be better than an original box and if you are just doing casual driving with an occasional trip down the strip, they would probably work out just fine.
Firm Feel's boxes, however, are worlds apart from the stock mush box and will feel about as close to a rack and pinion as is possible with a recirculation ball unit. They provide good feedback, are economical, and are easy to install. Combined with a longer pitman and idler and they can have the fast ratio to match a rack as well. Only drawback is these longer assemblies sometimes create header interference.
