This topic comes up with regularity, and the landscape is constantly changing, so it's probably time for me to once again update my current suggestions for Z System users.
Free is Okay
If you don't want to spend money, are only editing one image at a time, and don't mind some modest delays for some operations, then Nikon NX Studio is the raw converter you should try first. Based upon Silkypix, a well established Japanese raw converter, NX Studio is also the only raw converter that will guarantee that your raw conversion looks just like a JPEG would with your current camera settings.
The drawbacks to NX Studio are multiple: (a) it's slower than other converters at most basic operations; (b) it is still on the buggy side, and crashes are more commonplace than they should be; (c) if you're looking for AI and other advanced features, you won't find them; and (d) the documentation is poor and the UI is amateurish by modern standards.
That said, Nikon knows how to get Nikon results out of raw files. The "black box" of Nikon raw conversion in NX Studio is exactly the same as in the EXPEED chips in the cameras, and this results in really good results if you understand Nikon Picture Control Speak. The recent addition of pixel shift support (Zf and Z8) is arguably cleaner, simpler, and better than the other makers have managed.
Adobe's Lead Widens
Adobe has been using that US$10/month you've been sending them wisely. They're not just sitting on their hands watching your money compound at their bank. More so than any other company doing raw conversion, Adobe seems to be pushing all aspects of their product with regular and substantive updates.
Yes, AI is all the rage and that's getting added into Lightroom and Photoshop these days, but some of what Adobe is doing in this regard has made the clone tool a thing of the past, which produces better, more convincing touch-up results. Masking is now top notch and reliable. Two deep and broad products have gotten deeper and broader in their available tools and capabilities, pretty much exactly what any photographer who wants to keep current wants. Another benefit of using Lightroom or Photoshop: ubiquitous and excellent third party tutorials and documentation.
The primary drawback I find with Adobe's two converters is this: the color model and speed-oriented math they use in the background doesn't product the best possible results without some user tweaking. More so than any other raw converter I find myself adjusting color in my Nikon NEF files when using Lightroom or ACR.
If you're going to spend money on a raw converter, US$120 a year nets you a really good one (Lightroom and Photoshop's ACR). One that gets better with time. I know some of you dislike subscription models, but if you add up how much you've been paying for yearly updates to other non-subscription products trying to keep up with Adobe, you're going to find you're getting less for, in many cases, more money.
The Other Reasonable Contenders
I've been impressed with DXO recently. Their PhotoLab product is an excellent choice for someone who wants a really good default conversion (that they can still tweak). Coupled with the excellent built-in noise reduction choices and the library of lens corrections that go further than the maker defaults, you can go a long way with only a bit of fiddling with PhotoLab. Performance isn't the fastest in the world, but is acceptably fast on my MacBook Pro 14" (M1).
Capture One has long been a leading raw converter, mostly because of their consistent and excellent color model. At one time, I would have put Capture One a bit ahead of the Adobe converters simply because the results without having to tweak were better. However, it feels like Capture One now is asking for more money for less useful updating, so my recommendation has gotten more lukewarm over time. Still, it's a strong, well-supported product.
If you're looking for a bargain, Affinity Photo 2 is the clear choice. Essentially a Photoshop clone—without the AI—you can benefit from all the Photoshop instruction on the Internet for a very modest entry price (US$70). Serif, the maker of the Affinity software, is now part of a much bigger company, which is good news on the longevity front, which is where most software eventually has issues.
Macintosh users should also check out Raw Power (MacOS Mojave or later) or Nitro (MacOS Ventura or later). Created by the gentleman who headed up Apple Aperture, the US$100 Nitro is very modern converter that's nicely done, and can link in with Apple Photos to make for a true Lightroom challenger.
Whattabout?
Yes, I haven't mentioned a large number of other possible products to consider. They've all now fallen out of favor with me for one of a number of reasons: incomplete implementations, over reliance on AI features, burying the most used controls, constant upgrade nags, bugginess, performance issues, constantly changing UIs/choices, sloppy masking, and a host of other issues.
