My only concern about springs is that I'll be happy with them for a little while, but will want to go lower in the future. I don't want to mess with my suspension setup more than once, so that's why I'm kinda stuck between springs & coilovers. When I had my Nissan mini, I started with a 2" drop, and eventually the thing was dropped ~6" (ended up being about 3.5 to 4" off the ground)...

moral of story: I dont want to use springs and decide to go just a little lower later on, yet springs are cheaper and you don't have to mess with adjusting them...