There are a few threads about springs vs. coilovers, and there's a lengthy one about Swift Springs...the community who are going with springs are really liking this one. You've mentioned some of the pros and cons of both. I decided on coilovers b/c I could do less than 1" drop b/c the streets where I live aren't the best. In an ideal world, I'd like to be lower than 1", but in the real world, it's not practical. Plus, I wanted to corner balance my Z as I do go to the track now and again. There is a concern that if your shocks aren't matched to your springs, then you'd have excessive shock wear and etc, as you already mentioned, however I haven't heard any complaints or reports of such from the various spring threads I've come across.
Use the keywords "Swift spring review" in the search section and you'll find a "Swift Spring" thread with over 590 posts...ask there as you'll likely get a lot more responses and feedback.
If you have the budget, go with coilovers, if not, springs is the way to go.
