I recall that we showed you both Cambo and Arca options. We think both companies make great products. But based on your work and personality suggested that Arca was the better fit.
All the tech cameras are basically flat metal plates with the option to hang large format digital lenses in front of the sensor, and then move around a bit. They will all result in the same theoretical image quality. The question is really which ones favor the way you work. That's something only your own testing and/or a dealer that gets to know your needs and preferences can determine. Below are some things I love about the Arca Swiss tech line; not every item is exclusive to Arca Swiss (though many/most are):
Arca Swiss Focus- Giant custom helical that affords adjustment of focus that is many times more precise than the "HPF" ring Alpa adds to the Rodenstock/Schneider-made helicals
---- A/B testing is therefor far easier, as you can easily return to the A if you find it was sharper
---- Focus presets (e.g. hyperfocal or psuedo-hyper-focal or zone focus) can be far more easily and precisely set and recalled; 90% of the time I'm using an Arca I'm not "focusing" – I'm simply putting the helical to one of my presets knowing with 100% confidence what the resulting range (not just center, but front and back) of the focus will be
- Offset system that solves the same challenge as the Alpa "shimming" system, but in a way that is more field-change friendly and can be set up for more than one back (e.g. rental back, IR back, monochrome back) or wavelength in the case of IR imaging
--- For those that prefer ground glass focus/composition (I do not; preferring live view or focus helical presets) the Arca Rotaslide allows ground glass without removal
Arca Swiss Mechanical/Industrial Design- Rotamount allows rotation of back without removing the back, and without changing the location of the buttons/knobs of the body (since the body doesn't change; only the back)
- All movements (rise/fall/shift) are natively on the rear (the sensor moves, not the lens); no adapters required
- Tilt is built into the body and available for every lens and requires neither spacers nor special versions of the lens
- Strong interoperability with their view camera line. This is especially important in an era of ultra-high-res; with 150mp maintaining depth of field can be challenging (with a ceiling so high you have to work hard to hit the ceiling) and a bit of tilt can go a long way in many scenes.
Arca Swiss Handling- Back and lens can be mounted/dismounted with a single hand (especially nice when it's old and you don't want to remove heavy gloves from both hands)
- Grip that is grippy whether hot or cold, wet or dry
- The native camera mount is, an Arca Swiss dovetail and such mounts are both on the top and bottom of the camera
- Shutter release is in the bottom center; most of our users now use the sensor-based-ES, but on the occasion you want a physical cable release for firing a copal shutter, it will be in the place on the body least likely to cause camera shake
- Great two-plane lens shade that lets you set the front (which is what effects flare) while sliding the rear in/out for lens access, and swings entirely out of the way for lens changes.
- The smallest body ("Factum") is really an interoperable accessory to the larger body, meaning it's easy to own both and switch back and forth. Notably the Factum still has tilt/swing and one direction of shift/rise/fall.
Arca Swiss the Company- Extremely good historical track record of making their cameras/accessories forward/backward compatible. The "Arca Swiss style dovetail"? That's them,
many decades ago; so savvy, simple, and effective that it's now the most widely followed quick-release standard. They've been at this for nearly 60 years and it shows.
- Repairs and service are done inside the USA (no export/import/international-shipping) with exceptionally fast turnaround time
- Friendly, humble, honest, and easy to work with at the corporate level. Anytime we've had a disagreement with them (e.g. we thought something should be a warranty repair due to extenuating circumstances even though it technically shouldn't be, or the rare occasion we've thought something they made was not perfect) we've worked together to a very reasonable solution.
- Pricing based on the product engineering/manufacturing, not the demand. There is no luxury or hassle mark-up; this is especially notable on accessories such as adapter plates, which are very reasonably priced.
- Evaluation/Rental/Training/Service/Support are provided by dedicated dealers like DT. We have 25 full-time employees with offices in NYC and LA and a 100% focus on medium-format and the accessories surrounding them (Eizo/Profoto/Broncolor/Arca/Cambo).
Everything you need to know about the Arca Swiss technical line can be gleamed from their tripod head line. There are other tripod heads that are cheaper, flashier, nicer looking, or are better marketed. But the Arca Swiss Cube is the unquestioned King of Tripod Heads for landscape, architecture, and still-life shooters. The only tripod heads that come close to the Cube are the ones that are direct knock-offs of the Cube.
Notably, however, Arca is a small company of
craftsmen, a word that is wrought with overuse, but is, in fact, extremely rare to find today. They
don't have a website (sometimes people mistake the German distributor's website as being from the Arca mothership; it is not), produce only very limited marketing (basic informational PDFs with specs; even those only when we really pester them to), and are not owned/operated with the mentality of relentless growth and ballooning profit. They are very slow to release new products, but when they do they are extremely well thought out. They simply go about making
great cameras (and tripod heads) and enough people keep buying them every year that they can keep doing their thing the same as they have for the better part of a century. So if you're expecting an active instagram account, "collectibility", luxury branding, or a variety of rare woods to select from for your handle, then Arca Swiss is not for you. They just make technically superb, extremely modular and long lasting, ultra precise cameras.
There are plenty of nice things to say in favor of Cambo, Alpa, Linhof, etc. But DT stopped selling Alpa years ago and you asked this question specifically about Alpa and Arca, so I've answered in that context. I hope this helps you in your journey! Hopefully someone will chime in with some good reasons to consider Alpa so you can balance those into your consideration as well.
Whatever tech camera you get I think you'll love it. The IQ4 you own is unquestionably the
best back ever made for tech camera use. It's really created a surge in interest for tech cameras.