SUTime is very good, like all the StanfordNLP stuff. We chose to do Duckling because:

- To my knowledge SUTime only supports English

- We wanted something that's easy to extend. SUTime is somewhat hard to extend, especially if you are not into Java

- We needed not just temporal expressions, but also monetary data, temperatures, quantities...

That being said, Duckling is still young and certainly not as proven as SUTime yet.