I've seen people talk about the warcomps a few times- getting them stuck, and gas leakage- putting ports where the labyrinth seals would be makes the system less efficiently sealed, and more likely to carbon bind.  The RC2 is a really good can.  The RC2 and one muzzle device is about twice the price of a Recce 5 which comes with the muzzle device, and they compare really closely when you're running those both on a pulse system and observing muzzle flash, and comparing weight and size.  Gas in the face is similarly not a problem with either.  I think the Recce 5 has a better tonal sound than the RC2, and the RC2 produces slightly less impact to bolt speed.   The muzzle device options are more numerous and more affordably priced, and the supported thread pitches are probably more diverse with the Recce 5.  There are pros and cons to both.

Silencer shop's range report is running ~7-8DB louder on the Mini2 vs the RC2. That's making it seem like 1DB isn't the difference between the two models.

Mini2

RC2

Recce 5 tested better.

We ran the recce 5 against the RC2 on our pulse meter, and it didn't do as well as the silencer shop test with the handheld B&K, but overall par or bettered the RC2 in sound (we ran only one test string for video also so all cans were fairly represented).  Shortly after the video we did a little more tuning of the Recce 5 and pulled it down to 132 muzzle, 134 ear on the 16" 5.56mm MK1.  At that point it beats the RC2 in sound on both guns on the same pulse meter. That improvement also reduced backpressure, and muzzle flash a bit to the point I personally think the Recce 5 has lower flash than the RC2 granted we haven't done extensive testing, we're just observing the flash in low light.

The Recce 5 is a cool can- I can shoot a rubber block wall point blank indoors with no ear protection without ringing my ears. That's kind of a quantum leap in performance as far as I am aware in my 15 years in industry.  Again the RC2 is also very good.  I'm not a big fan of the mount, but I think the RC2 performance is highly under-rated in its present form.  The RC2 is better sound performing than all other industry 5.56mm suppressors I'm aware of except for the current production Recce 5.

Their tested Recce 5 was older before we took on a full-spectrum approach and did work to pull down shooters ear sound, but our latest version would probably test within 1DB muzzle of that test on their handheld meter because the pulse is ~132DB and is typically about 2-3DB louder than the 2209 or handheld meters on our template A weighted at max speed 262KHZ.

I wouldn't be too surprised if use had an influence on the test results.  They probably have a lot of demo rounds on their units, and the RC2 is probably significantly more popular than the Mini2 for demo events.  The RC2 has ~13 baffles, and is coaxial (tube in tube with design intent functional air passage between tubes) so it has about 3 times the surface area of a Recce 5 for heating per round and fouling to effect, and there are some very small coaxial flow features in it that might pack up and effect the sound performance and backpressure generation.  Our test was conducted on a brand new (unfouled) RC2 and brand new Recce 5, before our last tuning improvement of the Recce 5 which was influenced by the testing and being unhappy about the RC2 outperforming our can in one category.   Fouling is essentially the stone age version of PVD (physical vapor deposition) coatings, and fouling is probably a thickness per round, on all exposed surfaces, except the areas like the bore where the abrasive powder wears the buildup away over time.  

Also our testing standards are a bit different.  They (silencer shop) are mil-std ear using the handheld as far as I know (either right or left), we are using the pulse and Ase Utra style test settup with the ear mics on the shooters ears to tell people what's happening at their ears.  We are using Griffin MK1 carbines, they are using something else.

I have a 556 RC2.  It stays on my 11.5" KAC SBR and overall I'm very happy with it.  It sounds good, it's nowhere near hearing safe, but it takes the edge off and for me it's the difference between having to wear muffs and plugs or getting away with just plugs.  The mount hasn't given me any problems, I take the can off while it's still warm after shooting, and I use a Bootleg adjustable bolt carrier in that rifle.  It makes for a very pleasant, low gas setup.

ETA - don't get too hung up on decibel ratings.  It's still loud as hell to my ears, but so are all rifles shooting supersonic cartridges.  I've been fortunate that I have relatively good and undamaged hearing, and I like to keep it that way.

A warcomp won't get you to 16" with a 13.7" barrel, consider thread overlap in your calculations. A warcomp will get a 14.5" barrel to 16.1".

The suppressor weight is ~1/2 ounce heavier.  The mounts for the M4SD II are about 1-1.5 ounces lighter than surefire muzzle devices, so the system weight of the M4SD II is ~ 1/2 to 1 ounce lighter than the RC2.    The new ECO-FLO baffles are going in future M4SD II suppressors so they will have lower backpressure, and lower ear signature- probably half ounce lighter weight.  Before the DEA FAST team was disbanded, they selected the M4SD K over the Surefire suppressor after a T&E of the units.

The design has been changed the first cans with the flow through design were sold in January (30SDK's).  We can upgrade the cores it has a cost and requires blasting, cutting, re-coreing, rewelding, repainting but it can be done.  It's not something we really want to do (it isn't efficient or a batch process), but it is something that can be done.  I don't know what the cost is.  That would be a customer service inquiry.

I think elective cost would be about $250.  They have to cut welds, remove the core, re-weld a core with the new baffles, weld the core into the tube, blast, paint, cure and return ship.  I think the reason it isn't on a list somewhere is that it isn't conducive to productivity so it isn't work we want to solicit.