Hey Mark,
In the last month I've put in both an overhead distributed system and a point source system with a delay and subs into two very different types of churches.
The overhead system was that way for several reasons;
1) The ceiling was low 13' and the room was long 60', so even coverage from one speaker (or speaker cluster) was impossible. For the folks in the back to hear, that one box would have to be cranked pretty loud, causing bad gain before feedback etc.
2) They have a more traditional worship style. A vocal or two with piano/keys or flute type music, never drums or electric guitars. The spoken word was most important. There's no need for 18" woofers or big boxes because the program material didn't call for it. A well tuned system with 25 or so high quality 8" ceiling speakers did the job great.
As you mentioned, SPL was important and w/ overhead spkrs so close to the listeners, the system has to be barely turned up for every seat to hear clearly. Nobody complains how loud it is, but everyone hears clearly. I put a few ceiling subs in just to add excitement when they watch movies and what not.
It can be a bit strange to hear the voice of the pastor on stage coming from right above you, but the brain makes the adjustment quickly and after a second, most don't even realize where his voice is coming from, it just IS.
The second church was an upgrade from their previous system and they are gearing up for a more contemporary style worship (full band with drums, guitars, keys, choir) A big 'A' frame church made it perfect for hanging a big box Renkus cabinet that EASE showed us would cover the first 15-20 pews or so, but we had almost 30 to cover, so we hung a smaller delay speaker for the back rows. A few subs to round out the bottom end, a day or two of Smaart and TEF and they are rocking!
It's all about the right design for the right room for the right purposes. I feel bad now for selling JBL SRX cabinets & SRM450's with the generic 'these are GREAT speakers for almost ANY situation' for years at the Guitar Center when I now realize the true worth of real system design.
anyways, enough of me. Cheers!
Steve.