The only improvement I'm aware of with the taller balljoints (when used in an oem control arm) is an improved camber curve. Drawbacks (again in oem control arm) is you will want an offset upper control arm shaft or more shims (or both) to align properly, on some cars (especially header equipped ones) this can pose a problem.
By itself an improved camber curve is good but in everyday driving will not really manifest itself in a significant feel of improvement unless you push yourself hard in corners.
Now all that said, combine the tall ball joint (or tall spindle for that matter) with an aftermarket upper control arm designed to be used for that application and you will usually see greater caster adjustability, a design that doesnt require a thicker shim pack and the camber curve and you will begin to see the difference.
Its definitly a swap worth doing if you like tossing your car into corners.