A quick note to summarise my thoughts on this:
I think, relatively, there's more to this and other discussions on matters DIR and UTD that comes from the "DIR wars" than what I can personally relate to. Naturally so because I wasn't around diving at that time.
I wasn't around for the invention of the Aqualung either, so obviously, that first system doesn't effect me either on an emotional level.
Don't get me wrong, I might feel differently about it all if I were already a diver then, doing things differently back in those days, and all of the sudden, someone was telling me that I was in desperate need of a body bag as my next accessory purchase - but, seen in context, some form of reaction to the circumstances that be/were is very human, and understandable.
No fingers pointed from this seat, in either direction.
But context is often left out, and a lot has changed since then.
Either way, it doesn't prompt bashing some twenty years later.
One can say that UTD or any other organisation for that matter, do something that one doesn't agree with, for whichever reasons one might have. That's perfectly fine.
When it comes to Ratio Deco, it has evolved since the original version. The italian project found ways to optimize it, and so it was optimized. That doesn't mean it's broken. It has great advantages, which one might choose to utilize, or not. The same, by extension and relation, goes for standard gasses.
The heart of Ratio Deco is that it's a strategy, and can be adjusted. If I'm far away from the nearest chamber, remote in icy water and I'm not perfectly hydrated or a bit fatigued, I adjust. One would be hard pressed for an empirically proven deco profile that accounts for all those variables regardless.
Either way, if one is curious about it, it's worth learning about it.
The Z-system is another punching bag. Most of the bashing of it I've seen comes from people who haven't even trained and dived it, and fails to touch on the pro's and con's of it's use. Also in this case, there are advantages that one can choose to utilize, or not.
For some dives, a set of backmounted doubles is a good tool. For others, not so. But it is what it is; I simply cannot add an extra tank into the isolatable "loop" when I need to. So when we do a 1:3 decompression rate, we use the "perfect" tool 1/3 of the time, and indie singles 2/3 of the time. Many of the people quick to denounce the Z, denounce indies with even more vigor. It's a paradox.
The MX-rebreather also got bashings online, sometimes in the form of the most heinous language, people crying wolf, etc. Still zero fatalities.
From an organization that is - unless I'm mistaken - the only one who has managed to have any insurance agency sign them a policy, and with zero incidents, across the board.
It's a bit more nuanced than this discussion would let believe - it's almost, but not quite, like comparing a restaurant's gastronomical theme to the recipe of a single dish.
If you want to know about a system, be it gear or decompression, go talk to an instructor about it, learn it and then make up your mind. It'll give you a much more nuanced body of knowledge to make up your mind from, than anything I or anyone else pours out on an internet forum.
That's all.
