I'll give my opinion too here (I did it last year in a very interesting thread but don't have the guts to search now) : making it very short, comparing different situations/projects involving different types of noise to solve and taking price, time and efficiency into account, I came to the conclusion that Neat wasn't worth buying it for those who are not owners yet in 2020. The Spatial NR Enhanced mode is fantastic for a lot of noise reduction scenarios, provided you're not careless with it. And noise is one of those things you really have to see in motion to get an idea of its impact, which sometimes means needing to render out at least a portion of the timeline to see where you're 'at'. Being able to capture a noise print from your specific camera and use it as a starting point in Neat, is fantastic-but it did take me a long time to tweak, trial & error, etc. Neat Video is a very powerful tool and I used it to recover some dark images I had shot, where we had little choice with the lighting given.

(Note that this is a pay site, but I think the information they provide is worth the investment.) Marc Wielage Bowdach just did a fantastic half-hour 2-part video comparing and contrasting Resolve 16 TNR/SNR with the latest Neat Video v5 over on. I tend to have a couple of settings for day scenes / day interiors, and a couple of settings for night scenes, and I usually wind up using more NR for night, taking care to avoid artifacts. The more Luma NR you use, the greater the risk of softening the picture. The trick for me is to adjust it on a scene by scene basis, consider doing NR on one color channel only (like Blue, which tends to be noisy), and also adjust Luma and Chroma separately. In truth, the SNR Enhanced mode in Resolve - which they give you free with Resolve Studio - is almost as good and is already included. Their latest version is the best they've ever done and is made especially for Resolve.

Short version: I think Neat does a better job overall but a) it costs more money, b) it takes more time, and c) it's very tweaky and has a lot of settings you have to carefully adjust for best results. Bowdach just did a fantastic half-hour 2-part video comparing and contrasting Resolve 16 TNR/SNR with the latest Neat Video v5 over on.

Neat video reduce noise v4