Bingo, Yahtzee, we have a winner. Add the inherent errors that comes from relying on your compromised brain and you have only guesswork to go on.
I was trying to think about how to respond to Dan's reply this morning and decided to give it up.
In order to really compare RD to other ascent strategies then we don't need anecdotes and we don't need "faith". What we need is controlled scientific experiment. We've never had one and the population of RD users is so small that I expect we never will.
So where does that leave us?
Without facts to discuss then all we can do is exchange ideas about what we're comfortable doing. Dan is clear in his opinion. He has said a number of things that I believe can be summarized by saying "he has faith"..... he's a believer. In some sense this is no different than what a computer user does. I have "faith" in my computer. I cannot and I will not deny this.
There are so few of us who have actual proof that their ascent strategies are scientifically sound that we all -- every one of us -- eventually settle on a style in which they have increasing "faith" over time because of a mounting body of success. This is what Dan is mentioning in his context and what I would argue in mine as well.
RD is perhaps demonstrably more prone to errors (brain farts) and we've all hear the stories about divers who have been bent because their mental math was off. The computer can be off too as someone above pointed out when they paraphrased a quote that we used in the early 1980's, which is that computers are very good at rapidly making mistakes.
Of course, in the 1980's we didn't have the kinds of software certification processes for safety critical applications that we have now... but the basic idea that a computer is not infallible is something that I don't think anyone can deny.
That said, we now have "safety integrity levels". I don't know to what degree computers are tested but it wouldn't surprise me, given the risks that they are certified to SIL-3 or SIL-4. I work in the (light) rail industry and all of the safety critical software is certified to SIL-4.
Of course that doesn't say anything to most people but what it means in concrete terms is that a computer certified to that level (SIL-4 for example) has a potential failure rate of 1x10^-4 to 1x10^-5 (about 1 failure in 100,000 for incidental use). For continuous operation (like in my work) this rating means a failure rate of 1 in a billion.
So while the logic doesn't hold 100% what I want to suggest is that a typical certified computer will make an incorrect average depth calculation 1 time in 100,000 dives on average.
How many times have you been at the supermarket keeping track of what your groceries should cost in your head and then been surprised at the check out how big your mental error was? Was it 1 time in 100,000? For me, it's every time! I thought I was good at math. I studied a LOT of math and I can make mental calculations faster than most of my friends, which is a great party trick. But I never get it exactly right at the supermarket.
This ^^ is is one of the big reasons why I won't use RD. The other reason is because there is a total lack of solid scientific testing. That's two big strikes against RD and two big check marks on the side of computers. I personally don't need more than that.
R..