I Have used both Metaio and Vuforia :
in my opinion Vuforia is best option as a free of cost and good tracking. Here are some points:
Metaio
- With metaio you can develop very fast.
- Various tracking are supported e.g. marker, image targets, marker-less, 3D object tracking also.
- You have to code separately for iOS and Android.
- Paid SDK (Commercial license)
- You can play MD2 animations of about to 100 frames.
- I faced flickering in tracking.
Vuforia
- Development is sort of time consuming but once you developed an app , you cleared path.
- Tracking ImageTargets, markers, video playing, imagebuttons(this is not in Metaio).
- You have to code separately, but if you go with Unity you have to code Once.
- Now Vuforia is also come with pricing model on based of no of target scans.
- With Unity you can play Animation.
- Tracking is flicker-less.