An AI computer does not do much during a dive that an SPG does not provide....typically the additional info that you get is how many minutes of air tank you have left based on the computers calculation of your current consumption rate.
The real benefits of AI are after the dive:
[snip]
The problem is that AI is very easy to get used to and then you will not want to go back to using an SPG. I still dive with an spg but only because I am too lazy to remove it from my reg set and it is not an inconvenience to have it as part of my kit when I dive. I roll my eyes at the notion that some folk state that they are somehow "streamlining" their gear by eliminating a hose, or reducing failure points, etc.
You don't think having a Gas Time Remaining calculation done for you, that you can see in real time, is a "real benefit"? I do. Not everyone needs it. But, there are a lot of features on many dive computers that I think are a benefit, but that not everyone has a use for.
Why is it a problem to not want to go back to using an SPG? I don't want to go back to using an SPG. I have several extra transmitters as backups, so that I (hopefully) won't have to go back to an SPG. What is wrong with that?
In Steve Lewis' book, The Six Skills, he has a whole chapter on Trim. In their, he defines trim at its highest level of performance to include having a neat, tidy, uncluttered rig. You don't take anything in the water that you don't need.
I wholeheartedly agree with the concept of not taking anything in the water that you don't need.
If you are doing recreational (sport) dives and you have AI, then you do not need an SPG (but you MIGHT need a better, more reliable AI...). Further, anyone should be able to recognize that, minor as it is, having a hose coming off your first stage running down to a clip on your waist belt, or around to a clip on your chest, is an entanglement hazard. When you don't have AI, it's a necessary evil, as it were. So necessary and, for so long, with no other real option that our community accepts it without question (generally). But, if you think you could get hung up on something by having a little bungee cord on your wing, then surely you could get hung up on a hose that is 24 or 26" long (or longer) and runs from tank valve down behind your arm?
My first tech instructor called me out in class once for saying, during a presentation of a dive plan, "I didn't do XYZ because I was just being lazy and I thought it was not necessary for this exercise." He said that not doing something because I was being lazy is the worst thing he ever heard me say, as a diver.