The standout feature for me is how exceptionally natural the Neural2 and WaveNet voices sound. The audio output comes across as smooth and human-like, rather than robotic. I also appreciate the broad range of supported languages and accents, which makes it much easier to localize content seamlessly across diverse international markets. Lastly, the fine-grained SSML controls let us precisely tune pitch, speed, and pronunciation, so the voice output fits specialized professional video and media workflows.
It is easy to inegrate with already existing libraties and works with multiple programming languages. If you don't have NLP models available, the pretrained ones that Cloud Natural Language API has can do a really good job. I also found the abundance of documentation and tutorials really useful.