Tried all 3 - WINNER is... Interface and Voice Translation Iris, Answers Skyvi.
VLingo just seemed to translate my words into a google search. Great for that feature I guess. It was also a little slow. I can see it used for simple navigation on your phone but it is not Siri - more like a Microsoft version of Siri.
Skyvi gave me great complex but often incorrect answers. One reason is that it often translated my speech incorrectly giving me longer, complex and off topic responses. BUT, when it did translate correctly Skyvi by far gave the best answers.
For example, if I ask, "who is Michael Jordan?" Iris very quickly answers a professional basketball player, but that's it. While Skyvi says where Michael Jordan was born and that he is a professional basketball player and active entrepreneur, etc.
Iris has the best interface and translated BEST and FASTEST and the most accurately. It also answered simple life questions like how much caffeine is in a cup of coffee, how many inches are in a meter. However it's overall knowledge seemed lacking. I think it is a genius baby learning and learning. It is going to be a real winner in the future.
CONCLUSION: Interface and Translation IRIS is way above the others. Actual answers... Skyvi gave the best answer BUT ONLY when it translated correctly. I wish Skyvi used Iris's translator, then we'd have a winner.