Partially it's because this is a false dichotomy. The most efficient and safe system isn't something that erects permanent barriers between pedestrians and cars – because a system like this creates ugly cities and undesirable walking, cycling, and driving conditions – it's something that allows them to coexist safely, generally by making them slower, more visible, and more predictable.
I walk/run, drive, and cycle in NYC. In my view, the way NYC works in most intersections and roads is pretty close to maximally efficient. And it generally gets better over time, although it has occasionally gotten worse in the name of safety.
The things that make it that way include (1) mostly one-way roads, which makes jaywalking significantly easier and safer (2) mostly single-lane or dual-lane roads (3) well-tuned traffic lights with relatively brief cycles (4) relatively low speed limits that are brutally enforced with speed traps (5) an abundance of red light cameras.
The least safe parts of the city are those with more than 2 lanes of traffic, especially if it's bi-directional, and those with really poorly designed cycling infrastructure. My pet peeve roads are the ones that look like this:
| sidewalk | cycle lane | parking spots | road |
e.g. Grand St in Williamsburg, because this design makes jay-walking extremely dangerous. and it makes cyclists go faster than they otherwise-would, because of the (occasionally-enough-to-be-dangerous false) sense of being insulated from both pedestrians and cars.
The other major source of risks, again IME, are cyclists going counter-traffic on one-way roads, and people on electric-assisted bikes in general traveling >20mph.