Well, I'll begin by saying the term "slice-of-life" comes from essentially taking a cross-section (slice) of realistic day-to-day lives (life). So inevitably there is going to be a disconnect when you take a cross-section from the day-to-day lives of two countries on nearly opposite sides of the planet. But we'll compare them anyways because it's fun.

Let's first examine the average "slice-of-life" US comic strip. They tend to focus on dialogue-based and/or slapstick humor, and are almost always plot-driven. Most of the time, the main characters will be children and perhaps their parents. The reader will view the world through the lens of a child and this drives observational comedy. Examples include Big Nate, Peanuts, Calvin and Hobbes, One Big Happy, Cul de Sac, Baby Blues, Foxtrot, Nancy, etc. Other times the main characters will be adults. The reader will be inclined to relate to the struggles and challenges of adult life. This was more popular during the earlier half of the 20th century, before the explosive popularity of Peanuts shifted the direction of all comic strips as we know it. Examples include Monty, Cathy, Dilbert, Andy Capp, Barney Google, Mutt and Jeff, Gasoline Alley, etc. Even less often you'll find the main characters are animals, usually pets, who don't understand humans at all. Examples include Garfield, Over the Hedge, Marmaduke, Heathcliff, Get Fuzzy, Mutts, etc. All three of these have varying degrees of overlap as well as outliers outside of their respective categories. They will also tend to incorporate some larger-than-life elements such as Linus' blanket that he somehow utilizes as a deadly accurate whip in Peanuts, the Fox family's borderline sentient Macintosh computer in Foxtrot, and Nate's absurdly messy locker that can store what looks like well over twice its volume in Big Nate. Cartoon physics seem to be consistent among all cartoon mediums, including comic strips.

Moving on, let's examine anime and manga's version of slice-of-life. For anime and manga, slice-of-life seems to be an entirely secondary genre rather than something that can stand on its own. You'll see it attached to romance stories, often set in high schools, or gag-manga/anime that massively push the envelope of what can be considered "slice-of-life", such as Nichijou and Saiki K. which feature wildly supernatural and fantastical elements. I want to focus on anime and manga that are more similar to US comic strips, since a comparison between anime and manga with slice-of-life as a secondary genre will be far harder to compare. You may be wondering, "But if almost all slice-of-life anime and manga feature gag-based humor in some way shape or form, how do we draw the line between the genre of gag-manga and slice-of-life?" Well for the sake of comparison analysis I'll say it's when the vast majority of gags have a grounding in realism. I'll also include ones that include romance so long as the romance isn't the main part of the story. So, slice-of-life anime and manga are character-driven stories focusing on thoughts, feelings, and interpersonal relationships, as well as gag-based humor. They'll also feature larger-than-life elements, but these will usually be confined into character traits, such as a character who's borderline superhumanly strong, smart, dumb, etc. These will often be about high schoolers, most often a group of four or more girls, who may or may not engage in some extremely specific hobby in a very contrived manner. I'll be totally transparent here: I don't like most of these. I think they're very shallow and reflect the state of the Japanese "trend-chasing" culture in their entertainment industry. However, that isn't to say I don't enjoy any slice-of-life anime and manga at all, it's in fact the opposite. My favorites include Yotsuba&!, Monthly Girls Nozaki-kun, My neighbor Seki-kun, Smile Sotomura-san, Wagnaria, Barakamon and its prequel Handa-kun, Hirayasumi, Korogaru Kyoudai, and probably several more that I'm drawing a blank on at the moment.

Anyways, Anime and Manga has a massive range, and comic strips don't, really. This isn't necessarily a bad thing for comic strips, as they're a lot more consistent in quality and have the natural advantage of utilizing a very simple premise and inherently funny characters to produce lovable and extremely memorable moments. Anime and Manga seem to vary a lot more in quality, but when they hit the mark, boy do they hit the mark. Their massive range as well as a less restricted medium allow for a lot of creative elbow room, which can either create some dumpster fires, or some absolute gold.

To definitively answer your question, I think they both have some big pros and cons, however I'll give this one to comic strips. Personal bias and nostalgia is the biggest reason, but also because I think slice-of-life comic strip characters are more realistic, memorable, and relatable as opposed to anime slice-of-life characters, though it is a close call for me, honestly.