I have used a Cressi computer since 2001. I believe it was manufactured by Seiko, and is identical to Tusa IQ 600, Sherwood AWAC-1. It's easier to download the Tusa/Sherwood manuals than find a Cressi one online. (The different brands just have a different plastic faceplate). It's nitrox compatible, glows in the dark, and has no backlight (which I prefer). Uses Buhlmann, but depending on where you read the specs, a 9 tissue model most likely to save on computation, but results the same. I think it's a great simple computer. The only drawback is the numbers are kinda small and it's mostly found in a console mount. No safety stop warning if that matters to you (you just watch the dive time to do a stop).
I recently purchased a used Nitek Plus as a backup computer for a liveaboard trip. Uses Buhlmann 16, and I believe also manufactured by Seiko. Multi-day diving gave NDL's within a minute of each other. I'd say they were only sometimes different due to console vs wrist depth variations.
I think both are great options, and are a perfect pair. Wife has a Oceanic Veo 3.0, and the default settings give more NDL.
I may be selling my extra Tusa IQ 600 in the near future...
FYI: I think changing the battery on an all plastic computer like the Tusa IQ 600 with a plain round o-ring is easier than the Nitek plus with it's strange o ring seal. The Nitek plus had a little bit of corrosion on the stainless steel backplate that needed to be cleaned. Plastic is always a simple wipe-off, and a hardware store o-ring can be used in an emergency.