There’s no black or white answer to that. You’re going to have to do some research.
Who is your target audience? Where do they buy? How many books do their read and what are their buying habits? There are genres that suit KU while some do better wide. KU also tends to favour productive authors, although slower authors can do well depending on expectations for their niche.
When my books were with a publisher they were in KU and they did absolutely abysmally. For 4 books (each with a KENPC over 500) I had less than 1,000 reads/month. That’s the reason I was able to get the rights back, the publisher said it was a “dead” series and no one was reading it. They were right, kind of - it simply wasn’t a KU series. I took my series wide and made 6-figures that year.
These days Amazon US is only around 30% of my income, the other 70% is Kobo, B&N, iTunes and GP. I’m also selling all around the world. Amazon is the dominant retailer in the US but not in other countries. Keep in mind there are very few Amazon stores and dozens of countries can’t even access Amazon. KU is also very American-centric and my books aren’t One little feature of being wide that I love is the world map on the Kobo dashboard, it sticks pins in where you sell books. I find it amazing to see my books selling in South Africa, UAE, Phillipines, the Netherlands. I think I’ve sold in over 70 countries now just with Kobo.