You'll want to get your camber to be as close to zero as possible- with Stock UCA as you turn the camber adjustment bolts to increase the caster correction- you negatively affect camber ( its give and take as I understand it).
Also the angle at which the ball joint resides in a stock UCA on a lifted truck is generally close to its maximum articulation- so you basically add stress the ball joint and boot as the suspension articulates = shorter life span, torn boots, or worse, sudden failure. The benefit of an aftermarket UCA is that it compensates for the lifted angle, puts the ball joint closer to its pre-lift orientation for better range of motion- and allows for a predefined increase in caster correction with out sacrificing camber adjustability.
Also the angle at which the ball joint resides in a stock UCA on a lifted truck is generally close to its maximum articulation- so you basically add stress the ball joint and boot as the suspension articulates = shorter life span, torn boots, or worse, sudden failure. The benefit of an aftermarket UCA is that it compensates for the lifted angle, puts the ball joint closer to its pre-lift orientation for better range of motion- and allows for a predefined increase in caster correction with out sacrificing camber adjustability.