Definetely when needing an image target based AR experience, I'd go with Vuforia Engine, the implementation is pretty straightforward (at least when using UNITY SDK), it is well documented and there are plenty of examples to start with. I wouldn't recommend it yet for tracking objects or environments if it is for commercial purposes, because it tends to fail from time to time from my experience.
Spark AR Studio is used to create AR experiences for the Brand Partners. The AR experience is created so interactive that the user is attracted to use the filter many times
I have used Spark AR Studio for the first time to create AR experiences and it deeply satisfies me. I have never used other software similar to this. It is most simple and creative software which I have ever found till now.