I tried both (and a bunch of other options) when Nova broke from an update. They were my two favorites, but ultimately I found I prefer Niagara's navigation I think.
I find it gets cluttered with too many apps. After like 40 apps Niagara can become a bit long to scroll through, especially when i can't remember an apps names half the time lol
I might have to check this out. I'm not sure how I feel about it being search based. But I do like the GPL license and it looks like it operates smoothly.
Absolutely love Niagara. The most used shortcut is the Niagara button. A swipe up to get a new Firefox tab and I can do searches without having to interact with Google's apps
It's the floating action button in the bottom right. You can enable it in settings, and have a tap on it or swipe on it bound to two different apps or shortcuts. A shortcut I use it for is to open a new web browser tab to do searches.
I'm a fan of KISS launcher coupled together with Wallpaper engine. It's damn simple and it's only a swipe up to use the keyboard. Not to mention you can directly type in links, contacts, w/e and it just opens them! Highly recommended.