Anova has much higher power output especially on the larger (Wifi+BT) model which both speeds up the heating by quite a bit and allows you to cook large volumes.

Anova is also much easier to clean than the Joule, it comes apart so easily and you just dry it out, I have one for over a year and no signs of scaling on the heating element because of that. The joule on the other hand can't be easily clean you can unscrew the bottom but then you need to use a brush and the heating element isn't fully exposed.

I have them both, and tbh I use the Anova considerably more, it's built better, it's built smarter, and the fact that I don't need to use a phone is a huge plus.

Sure the phone is great for the first week if you never used sous vide before (I cooked Sous Vide on an induction cooker with very coarse temp control and use a thermometer to know when I should turn it off and on for nearly 2 years before getting a proper setup) but once you know the temp it just becomes a hassle.