Very few guest posts will even be linked to from the homepage. When choosing guest posts it's best to choose ones that will at least display your post on a main category page, so you have homepage->category page->your article.
And almost no real site displays full content on the homepage, so you are not going to get your link on the homepage. Any that do that are not real sites, they're guest post farms.
And even if your article appears on a category page, it will roll off. A guest post is just an article with no backlinks on a strong site. A PBN is a permanent in-content homepage link.
You would really see a contrast if you bought, say 5 powerful guest posts, the ones that cost $2k-$5k, forbes etc and compared that with spending $15k-$20k on domains then setting up blogs and giving yourself 5 homepage links. You would skyrocket with the pbn links. With the guest posts.. You'll get a boost, but it will be pretty pathetic. I've never met anyone who's been that impressed with top guest posts. Every agency client I have has said they didn't get good results with them, definitely not in proportion to the amount spent.
Normal mid level guest posts are good because you build up a more natural looking link profile, and you're ramping up your RDs, which is a rank factor when it's real links, ie, not just 1000 comment links, which has no effect on your RDs in Google's eyes.
You can also boost all your mid-level guest posts for an even stronger boost. They work, but it's just more expensive dollar for dollar. I'd say somewhere around $1 for a pbn spend is equivalent to $5 for a guest post spend. This is why PBNs are so damn popular, otherwise everyone would just be buying/selling guest posts

Guest posts mostly just sell well to the white hat/business crowds who are afraid of PBNs.
I would go so far as to say you shouldn't even bother with guest posts for sites making under $10k/mo. Growth to $5k, $10k, even up to $20k/mo is best done with PBNs, THEN to scale into the $50k-$100k+ area you need guest posts, because you can't just keep adding PBNs, and the bigger you get, the more exposure you get.