UniversalAR offers you more flexibility because it can be used with other frameworks and tools such as Unity and aframe. It’s not uncommon for clients to ask for an embedded webar experience in their website, and the way to do this is using UAR, although you can ask Zappar to embbed your ZapWorks Studio project for an extra fee.
UniversalAR also gets the latest features and upgrades while ZapWorks Studio tends to lag behind and get them later. The facetracking feature is much better on UniversalAR than on Zapworks Studio for example.
The advantage of Zapworks Studio is its ease of use. It’s a game framework for AR, so you have a nice GUI and wysiwyg features like the scene view, realtime visualization of animations, etc.
I see the studio has many integrated plug-ins for a button, and action support, that you can not benefit from using Unity WebGL. Including easy integration for image tracking and so forth.
Everything that you can do in Zapworks Studio you can do in Unity. Unity has the inspector, which allows you to attach scripts to gameobjects and depending on the case you barely code at all. Similar to actions but there are many more things. The difference is that Zapworks Studio already has a lot of stuff out of the box for AR, Unity does not. For Unity you only have the UAR SDK.
The main downside of Unity is build size. WebGL builds in Unity are heavy. Clients will often decline Unity because of it. Another point is that Unity does not officially support mobile WebGL yet. It’s kinda rough and you can run into various issues, but overall it works. Another downside…it takes 15~30min to build for WebGL, I’m not joking ;_;.