If you are deciding between the Perdix and Teric, the good news is, you should extremely happy with either one. Think of it as deciding whether you want your favorite sports car with a manual or automatic transmission.
For the poster above who writes that you might like the Perdix better for Sidemount than the Teric, I don't quite understand the reference since, as I write below, my best understanding is that they are functionally equivalent with the differences primarily in form factor.
However, the person comparing the other products did bring up a valid point in that Shearwater is adamant about not providing GTR across multiple tanks, so you may want to consider that product if that feature is important to you. I would also question that it also does "automatic gas switching" as that was a feature of the Cochrane's that was either loved or hated - depending on who you spoke with. Shearwaters do not automatically gas switch, but they do take optimal gas available into consideration when doing calculations. You can search for more detailed info on both topics.
When I was in a similar position, I had been using an Oceanic GEO 2.0 for over 150 recreational but decided to switch to a Teric when I started technical dive training in preparation for a 3+ week trip on the Odyssey diving the wrecks in Truk Lagoon this past July.
Of the 96 dives I did there, the majority were EANx with deco obligations including gas switching for accelerated deco on the deeper wrecks. I was with friends who were experienced tech and cave divers as well as others that were new like me to tech - most using Shearwaters - so there was much discussion between dives about gradient factors and other usage factors and settings. From a capabilities aspect, they are functionally equal.
With that background, here are more specific points to what you are asking:
I wear my Teric as a watch when I am on dive trips, but not for regular daily use. I wear it on my right wrist when I am diving and my left when not. Switching it when putting on/taking off my wet suit means it is always on my arm and not subject to getting crushed, stepped on, lost or stolen. It is therefore always with me to view surface interval, dive planning or log info without carrying it around (and remembering to take it) or adjusting straps to wear on my bear arm once out of my suit. And, if you do buy the Teric, get a Nato strap so that if a pin breaks your computer will only flop back and forth and not drop to the ocean floor - much like the Perdix uses double straps. Actually, buy two straps so you can use a second as an extension in case you need it for your larger sized suits. I got orange just in case, but I think it looks good with the black bezel.
I worried about battery life before my trip but was pleasantly surprised. Using a single transmitter, with 4-5 hours of diving per day, usage on the surface for surface analysis, dive planning, etc., with a brightness of Medium would consume around 20-25% of the battery per day. I tend to charge my li-ion batteries at about 50% so I would generally go 2 days or so between each charge, but probably could have gone 4 or more if I had to. I brought with me a 10,000 mAh wireless capable battery so I had the option to charge wirelessly if the supplied USB charging cradle failed for some reason during the trip. It also means that whichever charging method I selected, I could take my Teric with me and not have to leave it somewhere charging, which I usually did at night in my room, which was around 1.5 hours. On the Perdix side, I did read about people flooding the battery compartment for whatever reason, but felt that that was as likely to happen as an overall battery failure on the Teric - so in my mind potential battery issues were a wash.
I disagree that the Teric is more subject to glass scratching as I was intending to get a protective covering before my trip, but just didn't get to it. So I was nervous at first, but after all those dives on the wrecks doing every engine room, squeezing through narrow areas and sticking my hands in literally holds of bullets to lift them by the fistful I have one little dent in the edge of the metal bezel that you can see if you look for it, but no scratches in the sapphire glass. Far better than most of the used Perdix's I see offered for sale here with far fewer dives and maybe not even as challenging conditions.
For full disclosure, I have never used a Perdix. And, much as when we would discuss features and capabilities on the boat it sounded like we were talking about the same device, the menu systems just didn't translate the same. So I can only say that the Perdix did everything I expected it to do, and the menu structure was easy to navigate. But, I would expect a Perdix user to say the exact same thing. However, I could see where someone who was more familiar with one would think less of the other, simply because it was different than what they were familiar with and not because two buttons or four is any better or worse than the other.
Usually in comparisons, like some of the posts in this thread, it is pointed out that the display is bigger on the Perdix, has more information and is easier to read - but I think that is like the project management truism that says you can have your project done well, done quickly and done inexpensively, but you can only have 2 of the 3. It can be done well and quickly, but it won't be inexpensive, etc.
The Teric has a large font display mode with the minimalist of info, that is only available in Rec mode - if you have really bad vision. The Teric in normal size in the default configuration does have less info than the Perdix. However, as you can change the middle section to up to three segments including tank 1 and tank 2 into a single one of those segments (which I did not need or do) I had no problem configuring the device for something that worked well for me, even considering I was doing mostly deco and gas switching.
As I had plenty of deco time on the hang bar to play with the available info and settings I would move the tissue loading graph into one of the segments as that was one of the frequent comments I read in comparisons, or I would move the SurfGF to the front screen for a time. Doing this just made it more convenient since like the Perdix the Teric allows you to view additional info not on the front screen by scrolling through via button press. Though to be fair, I believe the Perdix can roll through the info with fewer button pushes, but I didn't find what I was doing was onerous.
My last point of customization is that you may never experience what you like until you use it a while - it has that many options. I read the full manual when I got it and started using it during my training and regular rec diving. Five months later I read it again during the plane ride over. I then read specific sections again over the three weeks and 96 dives as I became more familiar with actually doing technical diving and deciding better the information I wanted to see and where. And when I got back, I reread many of the posts on this board, especially from the Shearwater account that helped me understand even more minute details about configuration such as if you populate the three segments with things other than your current 02% it automatically moves to the bottom of the display, giving you almost a fourth customizable segment.
I should also add that my eyes will be 60 later this month and I had no problem reading the display even with it in Medium brightness.
Bottom line, you will be happy with either one.
And much like my fast, cheap, good truism, there isn't only one correct answer here either - just what works for you.
Hopefully the information helps you. I know I have benefited from what others have posted as I had decisions to make.
