The world saw some big and remarkable discoveries in the 20th century. Artificial Intelligence is one of them. There was a time when AI and Machine Learning(ML) could not be applied due to a lack of computing power. But today's computers are robust enough to handle Machine Learning algorithms. That's why AI and ML are ruling in almost every field.

Based on the summary, it's evident that Python is a better choice over other languages mainly because it being generic enough that it not just good for statistical/machine-learning related tasks but other generic tasks and having better support for all DNN frameworks like Tensorflow, Caffe. But, R can be very handy for a quick prototype that doesn't need to use DNN frameworks. So, to summarize, R is the choice of language for a quick prototype but for long term python is the choice of language.