Drop spindles vs. lowering springs

[astroracer]

What you want to consider is alignment after the drop. Drop spindles create (essentially) a static, straight down drop which doesn't affect the current alignment to a great degree. Lowering springs lower the car in relationship to the spindle which increases camber. To correct the camber the upper arms need to be pushed outboard with more (or less) shims. The only problem here is how straight your car is to begin with and how much "room" you have to correct the alignment.
I will go with dropped spindles every time to get the "majority" of a drop and then adjust that with lowering springs to dial it in. I feel doing it this way leaves more room for adjustment...
Mark