I own rEvo and Defender (X-CCR/Hammerhead variant) so I'll take a crack at the question. All of these points are debatable and just merely my opinion, not to be taken as gospel. I wrote this out in a draft, deleted my draft and then decided to re-write it. I know somebody is going to disagree and argue with me here but whatever..
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@mr_v I don't want to turn this into a "my rebreather is better than your rebreather" pissing match.
What does the Meg do that the Revo doesn't
To address this specific question. Personally I think the X-CCR, JJ and Meg are 3 of the better back-mounted rebreathers available right now. If I had to start over again I'd be happy with either of these units.
The Meg has very good flood tolerance and de-watering abilities similar to X-CCR / JJ-CC however front-mounted counterlungs that are standard on the Meg are easier de-water.
ISC has good customer support in USA. Naturally some people like supporting USA-made type of things. While there are service centers for the X-CCR and JJ in the USA I think some repairs may have to go out of the country. I could be wrong.
Honestly I am running on outdated information here but prior to Mares acquisition rEvo support royally SUCKED in the US. The plus side of the rEvo is there is no "head" that has to be serviced but there are battery boxes, counterlungs integrated into the cave, etc.
Meg has options for larger 8lb radial scrubber. I know there are larger rEvo radial scrubbers available but I've literally never seen anyone use them and don't even know if they are still available. It's pretty common for people on the X-CCR or Meg to run larger scrubbers. I'm one of those people that likes having a larger scrubber.
Meg / JJ / X-CCR are really similar designs. Any canister variant can easily use rack-mounted LP50s if you're into that sort of thing AKA torture / spine compression.
More modular. You can use a standard wing and backplate. I know you can do this on the rEvo with modifications because I did it but it's not as easy a "stock" There are multiple size canisters, scrubbers available here. Yes I'm aware there are rEvo standards, minis, micros..
Very easy replacement or repair of counterlungs on Meg, JJ, or X-CCR whereas the rEvo requires major surgery. Been there, done that on several units. At one point you couldn't even buy rEvo counterlungs in the US, you had to go through an authorized service center for the repair.
I've said this before on here but I'll say it again. It's simply popular to hate on the rEvo on this forum and other social media outlets. Part of this was due to the AddHelium / South Florida instructor drama but also people love to harp on the lack of flood tolerance on the rEvo
I still own a rEvo, still occasionally dive one but I prefer the design of other units. A lot of the people touting flood tolerance and de-watering abilities have moved onto the KISS Sidewider. A unit that has arguably has even less water tolerance than the rEvo.
