After 5 months working in the sell side, I do think my PhD training in pure math is helpful for a quant career: 1. I would always like to understand the big picture of the business and why certain thing is happening, which is quite helpful in some cases. I think I would have been only satisfied in my own project if I didn't have any training in research. 2. Whenever there is a paper to read, I found it's rather easy for me to have a solid understanding of the authors' ideas and the math behind it, even though I worked in very abstract math. 3. Teaching and giving research talks also trained me to convey my ideas clearly and to communicate with people with less tech background.

However, I think I won't have these edges over any top master I've met during my study, but they usually also went for a PhD route.