Niche edit or guest post?

Of course, When you compare the price between guest post & niche edit, niche edit is much cheaper than guest posts.

Niche edit - Old content or some times just a sentence about your website, three-plus links already exist in that post may be your competitors.
Guest post - Fresh content fully relevant to your website, Link only to your website.

If you have good budget then go for guest posts.

Both of working well now, But you need to decide which kind of backlink is necessary for your site.

You can use both the Niche edit & Guest post in combination.

I've never had much ranking success with niche edits, they just don't move the needle for me at all.
Guest posts on the other hand have moved me into the top 10 for many keywords.
However, I still use Niche edits for linking to the home page for general power and use guest posts for targeted pages. I would personally avoid 10 x niche edits for $399, and get one fat niche edit on a site with over 1000 referring domains plus traffic.