Yep, I've used both, Omega-T is better if you're not dealing with Right-to-left languages, as the output format is left-to-right and you'd need to do it manually. It is worth noting though that Omega-T works only with NVDA later than 2019.3, and does not work with jaws at least last time I checked. However, Why I say it's better is because the interface is really very very light, you can add Google Translate support without API, (I don't know about the legality of that, but the addon is on their official Omega-T addons website). and Omega-T is open source and free.
On the other hand, Fluency Now is a decent choice too, but I have several problems with that, first off the interface is really heavy and sometimes my NVDA keeps saying blank in the target interface, the only way to fix it is restarting the application. I'd have to do that at least once every hour and a half on average, which is of course not really convenient. I'd say this could rather slow me down than speed up my work as CAT tools supposed to help you. But as for the right-to-left languages support it renders a good format. The other thing I personally hate, is the paying system. It is a monthly subscription, while I don't mind paying for entertainment services or audio books like audible, music and TV services, but I see it annoying that they don't have a one time purchase option in such app that doesn't have new content and that is related to work, you might get a very few amount of work in one month and still have to pay the full month. Just such subscription system personally annoys me.
Long story short, both work fine, but they will be a bit different of the web interface you're used to, so if you need any help you can ask us here I suppose, and you have a 15 days trial from Fluency Now too if you'd like to test it.