JBL SCL-3 or JBL S4Ai?

I am setting up a home theater system and I'm debating what choice for the rear speakers.  I have a Krell UDP 4k processor with PS Audio Stellar mono amps for the front JBL 4367 and center JBL SAM3HA. The rears will be driven by a PS Audio Stellar stereo amp.  I currently have some old B&W DM17 limited standing in for the rears, but they are inefficient and clearly point out that better suited rear speakers would really make the system sing.  The problem is that I'm debating between the JBL SCL-3 and JBL S4Ai rear speakers which will likely be mounted in the ceiling (or possible the side).  Anyone know anything about these speakers and why one would be preferred over the other for a 5.1 system?  Any insights would be appreciated.  Thanks. 
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The S4Ai are more dipole/bipole designed speakers which have more of a ambient type of sound.

The SCL-3 are direct radiating and you will probably hear more detailed and higher impact type of sounds from this driver.  Since it is more "direct radiating", it's not going to bounce the sound off the rear/side walls to create a more "background" type of surround.  The SCL-3 is also significantly more expensive than the S4Ai.

I suppose it depends on your budget and what type of sound you want.  In my experience and opinion, the surrounds don't necessarily have to match exactly with the front speakers, but they must be close.  It's the front 3 speakers (left/center/right) that are critical to match as exactly as possible.  You could look at some JBL Synthesis bookshelf speakers, unless you wanted something that would be mounted 'in-wall" like your original 2 choices.

I guess this indicates two different types of uses for these speakers.  I'm wondering if someone has heard either one or both speakers in a system and their impression of which one might be a better fit for a JBL Synthesis system similar to mine.  I'm more interested in sound quality first and theater experience second.