By quant firm I mean either a proprietary trading firm (no outside investors) or a hedge fund (takes outside money), but not a bank.
I have a CS background but have self-studied in stats, and received mentorship from people with strong math backgrounds.
Main advantages of quant shops (doesn't apply to banks) over working at Google/FB/Netflix etc:
- small company size, startup style working environment, but big corp pay (or more)
- more varied/interesting work, e.g. mix of distributed data processing, high performance numerics, or performance optimization in latency sensitive code
- compensation paid purely in cash, no stock options/RSUs