no ads and more customizability. last time I checked (and I’ve been checking multiple times over the years), the official client didn’t even let me change the post and comment font size, which is by default too small for me. at the same time, I don’t need huge-ass cards for every post and switch view to just post title with small thumbnails. I can sort subreddits I follow the way I want to, with the ones I visit most frequently on top of my list. I can add labels next to usernames with notes about the users. when I’m writing a post, there are buttons that help with quick markdown formatting. the comment section has got colorful depth markers so it’s easier to keep track of the chains. even the UI integrates better with the rest of my OS. in comparison to that, the official app is a crippled mess that is only good enough when all you do is scroll through auto-playing gifs and videos, and it doesn’t even support some of the native reddit features (like opening categories of your saved posts - a reddit gold Premium feature) that the third party clients do.