1 - It's insanely easy to build a landing page once you understand the way pages are built. Changing and navigating certain design elements is also incredibly easy - you can set global design options and then change them in-page if need be. I genuinely like the way LL thinks about page structure - i.e. Sections, Rows, and Columns.
2 - There's tons of design possibilities with LL's builder. Everything from gradients, box outlines, image overlays, and embedded rich media. The result is the ability to create something insanely beautiful without ever needing a developer.
3 - It produces clean HTML / CSS - which paid media tools like AdWords and Facebook Ads notice when determining relevancy scores on the landing page.
They are small nitpicks, but the Landing Lion team is aware and are planning to tackle this in 2018. I wish there were more text formatting capabilities when building landing pages. It's a small ask, but I find I have specific text requirements at times and LL has a limited selection. It definitely doesn't hold me back from recommending it, though.
This is also on the roadmap, but the idea of having a global component or content item would be amazing - i.e. publish a content block somewhere and reuse it in other pages. When that content block changes, it changes across all other pages it's used in. The most common example would be a menu that acts as a global item.
It completely depends on what you're trying to accomplish, but if you're looking for maximum control, beauty, performance, and speed, LL will be for you!
Landing Lion comes with out-of-the-box integrations + the ability to POST to a URL - so getting data where I needed it has never been a concern of mine. Ultimately, it's always about the experience.
If you want building experiences to be fun, I would strongly consider LL.
Building beautiful, high-converting landing page experiences that are graded well by PPC providers can be somewhat of a challenge for marketers. Not in Landing Lion.
I'm greatly improving my demand gen and content marketing efforts by using Landing Lion - and the time I save building pages compared to their competitors is astounding.