I would do niether as far as UCA's go. You'll want to look into the SPC UCA's from SC&C and ATS's tall C5 spindles. That will correct the poor geometry the A-bodies have from the factory. You can use whatever LCA's you want. I'm using that, along with my stock LCA's (nothing wrong with them) for my new car. If you go with the ATS spindles, you'll need C5 (at least) brakes and wheels.
As far as your direct question goes, as long as you get the correct spring rates, you won't be dissapointed. They're a good way to adjust your suspension height, if that's what you're into. They really don't offer any advantage.