A comparison is challenging in that in our experience there are many different use cases. It all depends on which geographies you are interested in, and what level of accuracy, speed, data freedom, and cost you are willing to accept. I mean of course we can do query X on different services and say service A returns answer 1, service B returns answer 2, etc. But that's only useful if your queries look like X, and very often they don't. So it's difficult to say "service A is better". Much more relevant is which is better for your specific needs (and budget).
The only guaranteed way to know if a service will meet your needs is to test, hence why we offer 2,500 free queries per day for as long as you like.
Happy geocoding!