Stuff you might want which some entry level computers surprisingly lack:
Average depth - so you can calculate gas consumption.
Logging for more than a handful of dives - so you can be lazy about writing up your log book.
PC downloadable logs - so you can star at graphs and wish you could hold stops better.
If you can download your dive log to a laptop/desktop computer, then the computer software (I use Subsurface, which is free and works very well) will tell your average depth. If you have AI, then it will also tell you your SAC on a moment-by-moment basis all the way through the dive, plus your average SAC for the whole dive. If you don't have AI, you can enter your start and end pressures and it will still tell you the average SAC for the whole dive.
I have never consulted "average depth" on my dive computer. I'm not even sure whether either of my computers displays that. Probably, but I don't know.
Multiple Gasseses?
My tank has never been close to empty. Why do I need to know my SAC? Who really cares? Why do you think you need all of this stuff?
Please explain what problem each of these metrics solves?
He explained that knowing average depth lets you calculate your consumption rate. And knowing your consumption rate will let you plan a dive - if you so choose. I don't think it's a bad idea at all, even for basic recreational dives, until you have an experience base to, essentially, "know" what your consumption and bottom times will be like.
I agree with you that multiple gases on a recreational computer are total marketing hype.
To the OP: I seem to be ever the contrarian on the subject of computers for new divers. I was where you are 2 years ago. One of my earliest posts here on SB was about the Hollis TX-1 and the merits of going with that for a first computer. Almost everyone that bothered to reply gave me some kind of answer that fell into one of two categories: One, "that is way too much computer. Get something cheaper and simple." Or, two, "if you're going to buy a tech-capable computer, get a Shearwater Petrel." Almost everyone (but definitely not EVERYONE) said that AI is useless.
Being a newb who tends to question everything but then follow the advice of the experienced folks, I ended up not getting the TX-1. However, I did somewhat ignore some of the advice in that I did go with a wristwatch-sized computer with a wireless AI transmitter.
Now, in short, almost 2 years have gone by and I have advanced to the point of getting my first tech diver certifications at the end of this past April, and have been doing tech dives since. I bought and later sold a Petrel 2. At this point, looking back and assessing, I love my AI. I have used it on every recreational dive I have done and have now moved the transmitter to my tech diving reg set and use it to monitor my tank pressure and collect consumption data even on tech dives. My primary computer is a tech computer (but no longer a Shearwater) and my backup is the Rec computer (with Gauge mode) that I bought after listening to all the posters here. And I am back to shopping for a Hollis TX-1 to replace my Rec computer as my backup to my primary tech computer. So, if I had gone with my own research and instincts from the beginning, I would have gotten a Hollis TX-1, still be using it, and not be looking to replace it. Instead, I am still using my first computer and I have been very happy with it. But, it is not trimix-capable and that is the direction I'm heading now, so I want to replace it.
Many tech divers here have a mantra of "two is one. One is none." But then they dive with only 1 computer and use a written plan and/or tables as their backup. I am firmly in the camp of having 2 computers on every dive - for many reasons. 2 computers is good on recreational dives, but it is even better (to me) on tech dives. And I don't mean a computer and a bottom timer (i.e. a computer operating in Gauge mode). I mean two computers operating in Dive mode. Just my opinion, of course. All the reasons for using a computer at all are the exact reasons I want a computer I can use if my primary computer croaks during a dive. PLUS the ability to sanity check one computer against the other.
Also, with Recreational Trimix being a viable option now, I think anyone looking at new computers should at least make their own evaluation on whether they want their first computer to be trimix-capable. Some agencies that certify new divers won't even certify you to dive below 100' without using Helium. Others will certify you to 130' with air or Nitrox. Regardless, being a recreational-only diver and using Helium is now a very realistic possibility (though, not common, of course - and with Helium prices being what they are, not likely to become very common).
Bottom line: Avoid anything with an algorithm that is too conservative. One of the most common reasons that computers are for sale in the Classifieds is that the person found it to be too conservative. OTOH, you virtually never see a computer for sale because it is not conservative enough. Likely candidates for too conservative would be anything from Suunto or Cressi - just as examples. If you really think you might go tech at some point, then give some thought to getting something that will be really useful in tech. I.e. a computer that supports (at least) the Buhlmann algorithm WITH Gradient Factors (i.e. not just some computer that uses a "modified Buhlmann" or "based on Buhlmann" algorithm. That computer will almost certainly either support trimix or be upgradeable to support trimix, but IF you go that route on a computer you should confirm that it has or will let you add trimix support (i.e. set a percentage of Helium, in addition to setting a percentage of Oxygen). Then, with those criteria, get whatever appeals to you.
Here is a good read (with a lot of info on different models and their relative conservatism):
So you want to buy a new computer?
