Are they all basically the same? Kaw Valley, JAL linear,  Noveske Pig, KAK flash can,PWS CQB...?
Or are some designs noticeable more effective?

I'm not sure about the others you listed but I have been very impressed with the Kaw Valley linear comp I have on my AR pistol. Makes it a totally different animal to shoot with no more teeth jarring concussion and it really does push the noise forward away from you. Big difference believe me, the best $45 bucks I've ever spent.

I'm sure they all work well. There's not really that much to the functionality of the design. I have the surefire warden and it works well too.

I have the KAK flashcan's on two of my pistols.  Works as advertised at $25.

I'm surprised there's not more who have tried the brake/blast shield combo from Wilson Combat.   That is one that I am interested in hearing feedback on.

I have their Accu-Tac on every one of my rifles except one.  

No direct experience, but they don't put out junk.

I think it's relatively new to them.  Probably why there isn't much on it yet.

I have the BRT, Kineti-tech and Levang on different pistols (223/300blk,7.62x39) and they seem to all function well. Can't tell a noticeable difference between them.
Reports on the sound diverters with small holes to let some blast through

Most effective would be a suppressor, but not sure if it's an option in Maine. In CA we only have the "second most effective" options available...

The kind with an expansion chamber will be more effective, because they are actually really shitty suppressors (shhhh... don't tell the ATF) that also redirect the noise. Noveske, Bulgarian type, etc.

Is the KX5 the same internally as the KX3, only slimmer?  Or is it basically just a wide mouth barrel extension?

Which have expansion chambers?

Many of these may LOOK similar, but they do not perform the same.

Flash Cans do redirect the concussion or blast forward & away from the shooter, but not nearly as well as other designs.  They are more about the LOOKS vs the FUNCTION.  Linear Compensators and the Noveske Pigs (KX3 & KX5) actually do much better in redirecting blast & concussion away from the shooter.  Blast Shields from Surefire, Griffin Armament, Ferfrans, and others also do a good job taming things down.

I believe the Noveske has a baffle.

The two most effective blast reducers are 1) a 20" barrel, and 2) a silencer. Cut the barrel down to 10.5 or less, the pressure exiting the muzzle at least doubles from 12,500 to 25,000 pounds. Nature of the beast - you have half as much expansion room in the barrel to decompress the gases before release.

Therefore, if reducing the blast is a real concern, we wouldn't use short barrels, and certainly would screw on some kind of blast trap to control the high pressure wave and moderate it.

We choose differently, and we get to live with the 25K pressure wave exiting a nearly bare muzzle. As far as devices go, anything that releases that pressure directly forward with no side ports does better. If it's some kind of compensator with side ports with a blast shield over it, all you did was redirect that gas back to the front at the expense of another part over the wrong part to begin with. Added weight and expense to do the same thing as a linear doesn't seem cost effective on a gun meant to be short and lightweight.

Absent the silencer the next step is to moderate the sound impact at the ears. For the price of some of the extreme devices, plus a flash can mounted over it hiding it's looks and correcting what it does wrong, save the money and buy better muffs and plugs. It's really not about how cool the gun looks - it's just a bullet launcher. It's about how the user controls the impact and the results.

I know, that's not what we see with the number of offerings on the market place - however, check the military grade guns issued and you don't see any of that, for good reasons. It's like the 1911 - and the huge number of race guns sold for carry. Lots of hi performance looking parts that have serious downsides to street or combat performance, but the gunners all say they are too good to fail using them.

Not so much.

Narrowed down to the KAK flashcan and KAW Valley.  Both great prices.
Added the 223 Linear Compensator Nano 1.5" S&J Hardware. Like the smaller size.

http://simplethreadeddevices.com     Was hoping to see this mentioned for a review

Can anyone review the Spikes Tactical Barking Spider?

I decided on the KAW Valley. It's reasonably priced. Maybe I'll give the KAK a try some other time. I can't see paying more than $100 for something that may look cool, but is much bigger, weighs and costs a lot more and might be only marginally more effective.