I don't use those two. I'm a huge fan of Wipr for both iOS/iPadOS and macOS as the apps are regularly updated, receives regular blocking list updates, and seems to break fewer pages than some. Ka-Block! is super simple and never transmits data to any servers. However, it is only updated 1-2 times a year.
Both of the above only apply to Safari. You might be looking for a VPN/firewall service like Guardian Firewall which impact apps and browsers equally.
I really like Ka-Block as it seems to be a pure Safari ad-blocker for both macOS and iOS (meaning it cannot read the contents of your pages, only compare URLs to a JSON blacklist.) No additional privileges required, no separate app to install, no connections to a remote server etc. It does have some tradeoffs in that a small number of ads do sometimes get through, and there's no whitelist feature, but its speed and simplicity are worth it IMO.
Plus, the developers have the source on GitHub, which is a nice plus.
I like Ka-Block—it has exactly zero settings which means less time wasted fiddling knobs. (In the rare case a site fails to load and you really need it to, you can always do the long-press-on-reload gesture in Safari).
It lets some ads through because it focuses on killing only egregious ads and trackers, which is fine and supports sites that serve ads responsively. And it's open-source so you can audit exactly what it's doing, if you want.