I put SPC UCA's on this time, the two times I lifted before I stayed stock. Three reasons:
1) More adjustability if you need it.
2) I read if you go to wider tires they can rub against the stock UCA's.
3) I read aftermarket UCA's can allow better articulation, wheel travel.
An example about articulation, I had a Tacoma with the TRD Baja 2" lift kit. TRD designed it to work with stock UCA's but they specifically noted in order to get the full travel out of the shocks upgraded UCA's are needed.
I cheaped out before and didn't upgrade, did fine keeping the lifts to about 2", there was some difficulty getting the caster in specs. As said above some people don't care if caster isn't in specs because it doesn't cause abnormal tire wear but does cause a floaty/wandering feel to the steering at high speeds.
This time on the '08 I figured I'd upgrade, boost it up closer to 3" lift and be able to adjust the caster to what feels the most stable at highway speeds.