So a few, probably senseless, words from a rare species of Choptimus Europus:
I was in a similar boat, my main goals were photography as in silent no bubbles, travel friendly as not a fan of cold European waters, and being able to integrate this with my existing setup ideally as well, to avoid taking double sets of everything if I also want to do some OC diving.
I would say from a photography view I have also preffered eCCR - hands are already taken by the camera, no need to add more workload.
There is certainly a few breathers on the market that could be interesting, all already mentioned here really. From my perspective:
Triton - no eCCR option and seems one needs to DYI a thing or two to get it "better".
Halcyon - well was not an option then, interesting design for sure. Really liking the wireless features. Though if Halcyon then better you have a fat wallet.
xCCR - seems to be a new rage, could be an interesting choice as well nowadays..
Choptima - eCCR, well built, easy serviceable and replaceable parts mostly.
GBM - dunno, not much info about it, last time I've checked was still being developed.
AmEx - don't see the point of buying anything that cannot grow with you, plus once you get all the necessary extras, it will cost way more. Just nope. And if it has no water traps, its a big NOPE. And let's don't forget the social media drama that comes with it.
Dunno about Sidewinder, sidemount breathers seem a very specialist tools for a specialist application in a way. And KISS seems to be a bit controversial looking around the forums. Plus no water traps. And then you need to sidemount stuff, so not just simple recreational OC per se.
Back then it was Triton vs Choptima for me, and the latter won.
Now after a few years, and thinking about the points you are interested in:
1) Travel - damn awesome, that thing packs like a handbag. I usually carry the whole canister/electronics (and whatever I can stuff inside the canister) in hand baggage, and the bag/hoses in the checked but this is because hand baggage allowance absolutely stinks in Europe especially if you are europoor and already carrying another 14kg of camera gear... Being so light it is also quite easy to kit up if diving from shore - no need to put all this crap then walk - just get it to the water, kit up there. Similarly in reverse, way easier on your back.
2) Re-usable harness etc - again, amazing. All I needed was a few extra D-rings on the harness (though one could go ghetto) and a one extra hose on the usual reg i.e. to connect it as dill. But basically its the same harness. Less crap to travel with, more flexibility and it also makes it easier since this is pretty much the setup one dived for years already. Makes the whole CCR adventure a bit cheaper too, so more money to be spent on actual diving.
Was totally great when did a few weeks in Komodo with recreational outfit that allowed me to dive alongside (the one tech center there stood me out, though guess should have known it is going to end up like this, as I was warned about them. They do have a rep that reaches far....). Brought cylinder/sorb/whip, managed to find welding class oxygen supply and off we went.
Would dive from the same boat as rest of the rec divers, 1-2 morning dives with Choppy, then when oxygen ran low (supply was funny and no booster), just unclip the choppy, change computer to OC and off I go for another dive as OC. That simple. Was not taking much space on the boat neither, since Choppy is so small, so hopefully minimized the being the nuisance levels to other divers too.
Similarly last trip around Amed - CCR during the day, then grab the same gear, just change the cylinder, and head for a bonfire OC dive.
3) Camera - there is a bit of a chest clutter up front, but then if approaching something on the bottom, just go head down really, not that big of an issue. Where it shines (at least for me) is the fact that you have every button/valve up front and that you can carry "less" on the sides.
The first because its so easy to adjust/change/react to any situation, no need to look around back plus less "travel distance" for your hands, since those are already on the camera xD
Secondly - anything shallow is so damn easy, I love the fact that your Dil is also your BO, since all you need is that single cylinder, mounted exactly like you would during rec. Without stage all sides are free (for the camera!) Absolutley loving it, especially that some of the best dives camera wise I had were in the under 20m range actually.
Deeper? Again I feel its easier, watching guys on backmount having that extra side cylinder I really did appreciate having one less - say under 60 I again go with that cylinder on my back plus only one stage (so one side free, teehee!), deeper, twinset and two stages - again one less. Not saying its perfect, but I do like it.
All the above makes it somehow simpler in my mind. And I like simple, its the complex stuff that gets you in trouble.
Bonus points is the ease of assembly/disassembly - while all the backmount folks are still faffing about, I am ready and having another tea or already thinking about brewskis. And that is without cutting any corners.
Another extra point could be DiveCAN - Choptima is fully digital (5 pin) so in theory if Shearwater moves their behind one day (hopefully before we all retire...), this one should be super easy to use with the PyroScience sensors. Technically one can do a conversion now too, though its a bit more involved, maybe one day we can get it out of the box...maybe.
Closest instructor is in Eilat (Israel), so not too far, seen a few Germs being certified there. However there are also very good AND budget friendly options in Mexico (Playa Del Carmen) and Indonesia (Bali-Amed). And once you factor in the VAT "discount", this pays for your trip and the training
EAC cartridges are neat, but me thinks these are so popular over the pond because in turn the sorb is so expensive there. So it makes sense, when the price is close.
In Europe on the other hand sorb is about 3-4x cheaper and the performance difference is not that significant. Dived Choppy with 812 and 797, works fine with both. And it is really not that hard to pack the sorb well. That said, yeah cartridges are very neat - the ease of changing one is amazing.