Until there are better sensors the electronic controlled ccr's will continue to be unreliable and therefore very high risk. The channeling problem is greatly reduced with proper packing of the absorbent to make sure it is packed full and cannot work loose. There are many failure points, you might as well be an astronaut, the training and the attention to detail required is unbelievable when you get beyond the purely mechanical rebreathers with limited dive profiles. The weakest link is the human. One mistake can be your last. We just lost a decorated Special Forces combat diver who safely dove a mechanical rebreather his entire career to an electronic rebreather two months after his retirement. He was highly respected in our community and a fanatic for training and attention to detail. If a rebreather got him, it can get anyone.
Sorry for your loss mate. Never gets easier.
On the subject of manual vs electronic CCR, the failure modes of a CCR (as stated earlier) generally break down into what we call the 3 H's
This is Hypoxia (too low PPO2), Hyperoxia (too high PPO2) and Hypercapnia (too high CO2).
The first 2 are related in the failure scenario to malfunctioning O2 sensors, whether by user error (expired, flooded, uncalibrated) or a pure failure of a good sensor (S*** Happens Mode). A large part of CCR training is in managing the O2 readouts (what should I see, what am I seeing, what do I need to do about the difference) and that requires a lot of proactive checking and discipline to conduct checks routinely and systematically. Where a mCCR has an advantage in this aspect is that if you don't continually monitor, you WILL die even if the machine is perfect. With eCCR, they are generally pretty reliable so it is much easier to fall into the habit of trusting the machine and allowing complacency to creep in. This will get you hurt eventually.
The hypercapnia is related to the scrubber, and most of these are related to breakthrough ( overusing the scrubber so it is depleted or poorly packed leading to channeling) or bypass, where due to a change in gas path unfiltered gas is allowed to enter the diver's inhale side. These are usually related to missing or incorrectly installed o-rings or inhale/exhale valves. Again, almost all of these will be picked up by correct pre-dive checks and adherence to checklists etc.
So, the main question that, I suspect, is behind the OP, are rebreathers for you? Most of that depends on your personal mindset and attitude toward diving. Some questions for you:
You've set up all your gear on the boat, tanks open ready to don and splash. You have to go to the head, you are away from your gear for 10 minutes. Do you do a full recheck of all your gear when you get back?
You analyze your rented nitrox tanks tanks at the jetty and label them. You load the tank onto the boat and strap it down yourself. When you get to them to gear up you see that the tape has come off and there are no markings on your tank. Do you re-analyse? Even when you KNOW that tank is in the place you put it?
This should give you an idea of the mindset required to be a safe successful rebreather diver. Its no coincidence that a disproportionately large percentage of CCR divers come from an aviation background. The habit of , for example, restarting a 10 page checklist from the start because someone interrupted you in the last 2 lines, is the kind of thing that keeps you alive on the loop.
(All of the above are seriously simplified, there are a lot of other aspects to consider but these are pertinent to this discussion. Rebreatherworld.com is a good resource)