I can't remember the last time I even looked at my SPG during the kind of dive you describe, so there's that. And since I can see the SPG just as easily as I can see my wrists...I think you and I experience dive ergonomics differently.
For what it's worth, I clip the SPG to my left hip if I'm not carrying a large slung tank on that side, and can see it just by glancing back. If it's a deeper dive and I either want the thing right in my face because narcosis/speed of depletion at depth and/or I have a bunch of tanks slung on the left, I'll run it under the arm, clipped at the shoulder, and can see it just by glancing down. On my CCR, I run the SPGs for the unit over the shoulders and clip them off...the left side one with the LPI hoses. Again, just glance down, no grabbing the SPG required.
The D4 is somewhat, though not radically, cheaper. You wouldn't have caught me suggesting a $1200 Predator for rec divers, but SW has changed the Petrel's relevance to rec divers by making it a lot more competitive on price (we're seeing lower-level players like SP drop the price of less competitive computers like the Luna lately, and I suspect the Petrel's price proximity is to thank). For the OP, though, I don't see why a midrange rec computer's the way to go; either get something super cheap with a gauge mode, or go all the way.
Indeed, a $200 DG03 or similar would "meet his needs" too. But he's already said he's not looking for bargain basement, so this isn't all that important.
The D4 isn't easier to use by any standard of which I'm aware...the U/I on each computer is very different and the Petrel's is more intuitive. Try reading a manual for both and see. In terms of use while diving, the Petrel is going to offer more data in an easier to see manner without hitting any buttons, even more data more easily accessed by hitting buttons, and will allow for making changes while diving that can range from nice to safety-related. How, aside from AI, is a D4 "easier to use"?
I think your (3) and (5) points are the same...we get it, you think SPGs are a real problem to use and AI is great. There's nothing wrong with that, though I think it says more about your SPG configuration and diving than it does about much else...but again, the OP said he doesn't care about AI.
(6) amuses me...just a bit ago you said he could make up for the connection reliability part of AI by having an SPG.
(7) is interesting. The OP specifically asked about the Petrel, so you must have had some kind of bad experience with tech divers yourself? Personally, I usually go solo when I'm on a rec boat and never discuss my gear with anyone. If someone wants to know what I think of what I'm diving, they can ask.
