You're comparing apples and oranges here, the Marx boys were more tart but Stan and Ollie have their own a-peel. Both are head-and-shoulders above Abbott & Costello and miles above the Three Stooges. Yes, I said it, I must now forfeit my masculinity because I think the Stooges aren't very funny.
Anyway, L&H were nearly perfect for silent movies, but Groucho and the boys got word power from some of the best comedy writers of their era. Yet, Harpo worked wordless, and L&H's voices were a solid asset when the talkies hit, unlike most other stars of the silents. So... I have no idea.
Both are good at slapstick, but I think the Marx brothers quickfire repartee has held up a lot better. Laurel and Hardy dialogue seems a bit lugubrious by modern standards. And the surreal stuff was ahead of its time.
Here's another vote for the Marx Bros, as they were far more subversive with their humour, which appeals to me more. "We took some pictures of the native girls, but they weren't developed. But we're going back again in a couple of weeks!" Hell, you couldn't get away with a line like that today. I still watched all the L & H shows that they put on the TV on Sundays when I was growing up, and liked 'em.
If you have to ask... Maybe it has something to do with the unlimited B&W Saturday TV marathons of Laurel and Hardy of my childhood, compared to the admission-paid Marx Brother's midnight movies of my teenage years.