You've seen my answer before, but I'll post it up to get conversation going.
I did coilovers for a couple of reasons. One I could tune the spring rate, the lowering springs are a set rate and what you buy is what you get. You can get coil overs in 50# rates incrementing from 150 up to 700#. The choice in shocks for coil over set ups is tremendous and adjustability is there as well.
I thought I'd change ride height more than I do, however having adjustability allows for corner balancing and getting the weight transfer just right.
I believe the better choice for the street and normal driving (with the looks of the drop) is a set of good quality progressive springs. That being said, like anything I put into my suspension, I don't cheap out -- I'll go with a US company that has good support, a good track record and history to go with it.