The first thing to note is that a cable break is NOT considered an emergency. I was always told a 1% launch failure (usually cable breaks) was par for the course.
Safety-wise, in many ways, winch launching is much safer than aero-towing anyway. A winch launch can be split into 3 phases:
- Enough runway left to land straight ahead
- Overlap: Enough runway to land straight ahead AND enough height to complete a safe (if abbreviated) circuit
- Enough height to complete a fairly normal circuit
If conditions (wind strength/direction, winch power, runway length) do not provide a sensible overlap then the duty instructor will not allow winching.
Compare that to an aero-tow - in the early stages (once you can't land straight ahead) you often don't have enough height to pick a perfect field/return to the airfield.
OC619