Missed this thread, but FWIW, I had two Heinrichs-Weikamp computers, an OSTC3 and and OSTC plus. They were similar and were upgraded to Trimix software. The main difference was that the OSTC 3 had magnetic buttons, and the Plus had piezo buttons like Shearwater. The magnetic buttons worked better with gloves, and the piezo buttons
on mine, although adjustable in the menu, did not work as well as the Shearwater ones (Have a Perdix now).
The crispness of the OSTC display is a league above what I have seen in comparable computers. It is readable at a greater angle due to bonding the display to the glass. Fantastic... Only the SW Teric is as crisp, albeit smaller (I had it before the Perdix). I have not tried the Peregrine though. The menu logic of the OSTC is really great, and it has many options to customize, including a super-large font mode.
Heinrichs-Weikamp include a Bühlmann calculation for "do not fly" times. SW do not include this as they say it is not realiable. Shearwater is in touch with hyperbaric experts and I take their word for it, but Heinrichs-Weikamp state Bühlmann wrote the ZHL16 algorithm specifically to work across pressure ranges including high altitude and flying. I thought it was great to have this feature on the OSTC. It is a tech computer so the user is supposed to use some judgment and not trust numbers blindly. I'd rather have do-not fly estimates included than VPM...
A Perdix has the board inside a dry sealed nylon housing, and the battery is in a separate compartment. The OSTC I had consisted of an aluminum frame that only housed the battery in a dry tube like the Shearwater. From memory, the electronic board seemed to have been potted in epoxy and bonded to the display glass, and placed in the open frame. The bottom plate was held by two screws into the epoxy, if memory serves (and I don't know if this applies across models).
What I like about the Perdix/Petrel is that they seem more reliable than any other computer, and like on the OSTC you can change the battery yourself (a feature I now absolutely insist on). The Perdix has a rounded underside, which is nice because human arms are also round in profile
so the SW computer tends to stay put... I find straps better than bungees, btw. The OSTC is flat like an iphone and tended to shift in position more. I was going to have a rounded base milled for mine.
Both Shearwater and Heinrichs-Weikamp have great customer support and are pleasant to deal with when ordering or for questions. Others documented generous warranty response for both.
Now that I live in the US I use the Perdix, which has a similar menu as most CCRs. If you want best readability, consider the OSTC4. Larger housing, but amazing display. The new(ish) OSTC Sport seems great, it takes a strap and has the magnetic switches again that will be very robust, but not sure about placing an analogue compass next to it, as I habitually do (except with the Teric: best compass I have ever used).
(Btw, and off topic: I have a hard time reading any modern black display in bright daylight in shallow water, even in bright setting. Always need to shade with the other hand. Great in the dark, but during the day the old displays were better and made batteries last an order of magnitude longer.)
